For gaming with add-on graphics, the advantage would be in Intel's favor in most game benchmarks.
If you run stuff in the background while gaming, they should end up roughly even.
The latest review shows in most scenarios that A10 and A8 Trinities beat the i3 2100 in Productivity, Media Encoding, Rendering and a lead in Gaming even @ 1080P. But yea the difference isn't day & night except for gaming.
The A8 is similar to slightly better in everyday tasks and raw compute. However, the biggest gain is that the integrated graphics is really good. This means that for medium low settings and resolutions you can play most games without a dedicated graphics card.
If you are going to use a dedicated graphics card then the i3 or i5 are better choices
InvalidError +1 mate.
If you are getting a deticated Graphics card then you really should consider a quadcore Athlon II, I think it will be a bit better for gaming in the near future since games are becoming more Multi-Threaded. If you are just doing basic gaming and web surfing, the A8 will do the job, and in Heavy gaming the I3 beats it because it's cores are very effecient. Otherwise in raw performance the I3 should be the winner by a fair share.