The point of the site is to show current Android and iOS users that their favorite apps are also on Windows Phone – or, if the apps aren’t available, to suggest similar ones that are. The site is powered by Berlin-based Xyo, which we last covered under its former name Xyologic.

Xyo is an analytics firm that, after selling its services to support two quiet years of development, went public in August with an multiplatform app search service.

The company is relentlessly keen to point out the limitations of the search services used in Apple and Google’s app stores – and it has a point, as most people only ever discover a limited set of expensively promoted apps. This is why the big numbers thrown around by Apple and Google about their app store populations are largely meaningless. Xyo tries to sidestep this state of affairs by presenting many genres and subgenres of app, so lesser-known apps can surface.

Nokia will be promoting App #Switch in retail stores and on Lumia phones themselves, and will also be using Xyo as the international app search provider for its Welcome Home content-importing app for PC and Mac.

Xyo is understandably using the opportunity afforded by the Nokia deal to big up its wider services. The company claims to have seen a pretty high install click rate from users since that August launch.

“22 percent of our users intend to install an app directly from Xyo.net,” CEO Zoe Adamowicz said in a statement. “That’s good news for our search product — it shows that a large percentage of users find what they are looking for. But it’s also great news for the whole industry: It shows that there are great apps in the app stores and users are keen to install them — they just need better tools to find them.”

For app discovery companies such as Xyo, partnerships are probably the most sure-fire way to bring in cash – data-wrangling is a special talent and in great demand these days. See also, rival Quixey‘s Ask.com partnership, announced a couple days ago.

To be frank, the Nokia deal doesn’t reflect terribly well on Microsoft. The whole point of Xyo is to make up for the failings of the standard app store model, and bringing Xyo on board in this way smells like a tacit admission on Nokia’s part that customers may not be able to easily find what they want on Windows Phone – even if it’s there, somewhere. That’s not to say Windows Phone is worse than its rivals in this regard, just that it’s apparently not better either.

But you never know. Nokia’s post-China-Mobile-deal share price bump yesterday may reflect an alignment of stars for the Finnish firm and for Windows Phone as a whole. If data-driven services such as that provided by Xyo help accelerate takeup, then all the better.

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The company said, somewhat controversially, that Apple’s app search was lacking, leaving users largely dependent on Top 25 lists that tend to reflect the size of the developer’s marketing budget more than they do relevance to the users’ needs.

It’s not the first time someone has highlighted a problem here. Indeed, there are a few companies trying to target a perceived need for app discovery. Appsfire and Quixey spring to mind, as – of course – does Chomp, which Apple bought earlier this year.

But another service that has been gearing up for around two years is Berlin-based Xyologic, whose Xyo service went into closed beta on Thursday (you can request an invite here).

Xyologic’s big selling point is the way its technology classifies apps into relatively specific genres – a strategy that it says makes it possible to understand even vaguely-expressed search queries. In a recent blog post, the firm said its work so far has shown:

• only five percent of app search queries are for specific usage functions.
• a similar amount are for specific app names.
• the vast majority are category searches.

So, using its proprietary ‘natural app category’ tech, the company has defined more than 700 app genres and more than 100 game genres. It also claims to “put some of the best and often undiscovered apps on top of the search result rankings”, and says it can make it easier for users to evaluate the quality of an app.

Right now, the Xyo beta covers Android, although iOS is coming soon. Xyologic also announced a funding round (amount undisclosed), from investors including Signia Venture Partners, Gameforge founder Klaas Kersting and Soundcloud co-founder Eric Wahlforss. Xyologic CEO Matthäus Krzykowski told me:

“This is the first app search that aims at the mainstream user. Our approach is unique in this sense that, in the last two years, we have gathered information on how users search for apps, what queries they type, how they behave.”

So how bad is the app discovery problem, really? According to Krzykowski, 0.1 percent of apps get 50 percent of the downloads.

“The situation is pretty similar on all platforms, albeit slightly better on iOS,” he added.

Sure, Krzykowski has a vested interest in pointing this out. But, at the same time, this kind of information is what’s kept the company afloat during its initial, pre-launch two years of operations. Until this new investment round, Xyologic has bootstrapped and supported itself by selling data and reports.

“We also tested older versions of our app search in partnerships with third parties where we split up the advertising revenue. We used this money to fund our innovation in app search,” Krzykowski noted, adding that, in terms of future revenues, “you will see innovative approaches to app marketing”.

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Google and its partners have never said how many Google TV devices were bought by consumers since the platform’s debut, but the company said in the past that device activations have doubled since the  Google TV 2.0 software update late last year. A Google spokesperson declined to comment on any numbers for this story. However, there are some very useful clues hidden within Google’s Android Market statistics: Google publishes ballpark numbers about each and every app’s active install base — the number of devices an app is installed on right now — as part of its Market app pages.

Google TV comes with a number of pre-installed apps, which are also listed on the Android Market. One example of this is the TV and Movies app, which is basically Google TV’s programming guide — an essential part of the Google TV experience that most users wouldn’t dare to delete from their machines. The active install base for this app, according to Google’s Android Market, currently is 500,000 to 1 million. The same is true for all the other apps that come pre-installed with Google TV, which suggests that the number of Google TV devices that are currently being used by consumers is less than 1 million.

This data is supported by findings from Xyologic, which recently estimated that the install base for various preinstalled apps ranges from around 600,000 to 900,000 devices. I asked Xyologic co-founder Matthäus Krzykowski how the company gathers its data, and he told me that it estimates the install base of apps based on a number of data points, and usually only sees error margins of a few percentage points.

It’s worth pointing out that the number of active devices doesn’t necessarily translate into sales numbers. People could have bought Google TV devices and never turned them on. Devices that haven’t received the Google TV 2.0 update, which was rolled out last fall, also aren’t part of any Android Market data.

Data shared by developers shows that Logitech's Revue makes up for up to 70 percent of all Google TV devices. The other two entries shown in the chart represent Sony Blu-ray players and TVs.

Still, Android Market data does offer some interesting insights into Google TV’s usage. App developers can, for example, see on their internal Market dashboard which devices their apps are installed on. I asked a few developers to share these data points with me, and the results show that Logitech’s Google TV fire sale apparently worked: the Logitech Revue set-top box accounts for 50 to 70 percent of all Google TV devices used to install various third-party apps, depending on who you ask.

That’s actually good news for Google, which is about to roll out a second generation of devices with CE partners like Vizio, Sony and LG. The new devices are based on ARM chips as opposed to Intel, which should bring the price down considerably. Logitech ended up selling its Revue set-top box for $99, which may just be the pricing sweet spot for a Google TV box.

Still, the numbers clearly show that Google has some work to do. Even if you take into account that active devices don’t equal sold devices, it’s obvious that others have been doing far better. Apple has sold 4.2 million Apple TV units, and Roku — despite missing its own sales goals — was able to sell 2.5 million boxes by the end of last year.

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Why is that the case? The conclusions can be interpreted in a couple of ways: it could mean that the gaming experience remains better on Apple’s devices than it does on those built using Android.

Or it could just be because games publishers are still putting iOS first in their priorities when developing games — specifically free-to-download games. That could be because research seems to indicate that iOS remains a better revenue driver when it comes to services like in-app purchases — a key route for games publishers to make money. (One recent report that highlights in-app revenues on iOS versus Android is a report from Distimo published yesterday.)

On the positive side for Android, the conclusions seem to indicate also that the Android Market provides a better opportunity for non-games publishers to have a hit app, while on the App Store, it’s harder for those publishers to get as good of a look in to the top rankings — and that is significant, since those rankings remain a key way for new users to discover apps on their devices.

Xyologic’s latest report notes in 2011, the Android Market saw more games downloads than it did in 2010, but non-gaming apps continued to account for the majority of downloads. In November 2011, there were 85 apps in the Market’s top 150, working out to 91.5 million downloads; and there were 65 games, with a download total of 33.42 million.

Those numbers show that the non-gaming apps were actually also more popular on a per-app basis: the average per-app downloads for non-games apps works out to 1.08 million; while for games it was just above 514,000.

Apple (NSDQ: AAPL), meanwhile, saw a smaller volume of downloads compared to Android — unsurprising given that Android has a much bigger installed base now than Apple’s iOS platform: within the top 150 downloaded apps, 50 were from non-games publishers and worked out to an average of 512,000 downloads per app (25,640,000 in total). The remaining 100 most popular apps were games, with average per-game downloads of 715,700 (71,570,000 in total).

The Top 25 Downloaded Publishers on Android in 2011, according to Xyologic: Google (NSDQ: GOOG), Facebook, Rovio, Adobe (NSDQ: ADBE), DroidHen Casual, Outfit7, Magma Mobile, Glu Mobile (NSDQ: GLUU), Go Dev Team, Kittehface Software, Skype, Notes, Nikolay Ananiev, Swiss Codemonkeys, NHN Corporation, Yahoo (NSDQ: YHOO), Handcent, Pandora (NYSE: P), Al Factory Limited, Kaufcom Games Apps Widgets, Verizon Wireless (NYSE: VZ), Runnergames, Backflip Studios, Polarbit.

The Top 25 Downloaded App Publishers on iPhone in 2011: Glu Mobile, Gameloft (EPA: GFT), Big Fish Games, Rovio, Capcom, Chilingo, Storm8/(TeamLava), Outfit7, Electronic Arts/Electronic Arts (NSDQ: ERTS) BV, Gamevil, Halfbrick Studios, DeNa/(Backflip Studios/Ngmoco), Zynga/Newtoy, NaturalMotion, Pocket Gem/(Streetview Labs), Tencent, NimbleBit, PopCap, Playforge, Clickgamer, Com2uS, Burbn, Orangenose Studios. It’s notable that the only non-gaming publisher here is Burbn, which makes the photo-taking, -filtering and -sharing app Instagram.

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Non-gaming apps on Android generated 91.5 million downloads in November compared to 33.4 million for games. Meanwhile on the iPhone, games in November generated 71.6 million downloads while other apps received 25.6 million downloads.

Android was actually even more tilted in favor of apps in 2010, with 116 of the top 150 apps being non-games. The iPhone used to be more balanced with 79 of the top apps being games compared to 71 percent for non-gaming apps.

Now, all but one of the top downloaded publishers on iPhone are gamemakers except for Instagram maker Burbn. On Android, the top 25 developers on Android were a mix of gaming and non-gaming publishers with Google at the head of the class. Google only had two apps on Android Market in 2010, Google Maps and Google Sky, but now the company has many more available on Android.

Here’s the list of the top 25 downloaded publishers on Android in 2011 according to Xyologic:
Google, Facebook, Rovio, Adobe, DroidHen Casual, Outfit7, Magma Mobile, Glu Mobile, Go Dev Team, Kittehface Software, Skype, Notes, Nikolay Ananiev, Swiss Codemonkeys, NHN Corporation, Yahoo, Handcent, Pandora, Al Factory Limited, Kaufcom Games Apps Widgets, Verizon Wireless, Runnergames, Backflip Studios, Polarbit.

And here’s the list of the top 25 downloaded publishers on the iPhone in 2011:

Glu Mobile, Gameloft, Big Fish Games, Rovio, Capcom, Chilingo  Storm8/(TeamLava), Outfit7, Electronic Arts/Electronic Arts BV, Gamevil, Halfbrick Studios, DeNa/(Backflip Studios/Ngmoco), Zynga/Newtoy, NaturalMotion, Pocket Gem/(Streetview Labs), Tencent, NimbleBit, PopCap, Playforge, Clickgamer, Com2uS, Burbn, Orangenose Studios.

This might not be news to some developers, who are aware of the relative strengths of each platform. But it’s interesting to again see how each platform differs, where the trends are going and where the opportunities lie. The iPhone is really becoming a powerful gaming device, but Android is more of a broad provider of utilities and services.

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