Maybe it is just me but whenever anyone compares WP8 to Android and iOS can calls WP8 immature, while they may be technically correct, it is an inaccurate comparison to compare two OS that have been around for 5+ years to one that has been barely 2.5 years.
Kinda like someone climbing into an Amish buggy and asking the driver where's the AC, OnStar button, heated seats and GPS. No, we haven't added THAT stuff yet.
WP8 is barely 5 months old. With such a major revision to the platform, unless MSFT was co developing every app with every develop simultaneously, of course there will be less apps on WP8 at the moment. Guess people forgot how barebones the Android Market was, and how the better core apps were on Cydia than in the App store. Where was the clamor for Instragam and Temple Run back then?
So OP, my history lesson/rant aside, play with both devices. Their hardware is similar enough...your choice is between a ton of apps, good resale value and a great vehicle for content that keeps its hands in your wallet...OR a cheaper, well supported device with expandable storage, wireless charging and a new take on how your phone can help you get things done socially.
You cannot lose either way. We hope you pick the 810, but certainly understand if you didn't.