You basically need to choose 3 things:

1. Ecosystem, iOS or Android. Sounds like you don't care, so get Android (cheaper and more options)
2. Size, which seems like you want something pocketable, I'd still opt for a min. 720p and preferably 1080p display
3. Performance, as in how many cpu cores, how much memory, seems like a non-issue. You'll want at least 4 cores and a gig of ram or you might start pulling your hair out.

So, here's a couple options

http://www.gsmarena.com/results.php3...Sversions=2600