CAT-THE FIFTH: I am one of the people who is still running an old 9800 admittedly with a bit of an overclock (nothing too fancy) and as my monitor is only on 1600 res it can happily cope with virtually all the games I play. You can get a lot out of a cheap discrete GPU, much more than even the best of the IGPs. If casual gamers are playing very modern games (that is a very big if, surely if casual they are more likely to be playing older games) then no matter whether you prefer AMD or Intel, you would do better by spending £120-150 on a graphics card. Now I will happily admit that the AMD IGP is better than Intels but the issue becomes one of is that performance benefit actually worth it:
1. If both Intel i3 and AMD A8 can both run a game but at less than 30 fps, the fact that AMD is faster is probably of limited interest because most people would regard as neither being playable.
2. Maybe it is just me but on a laptop screen I cannot tell the difference between AMD or intel on video playback
As for battery life if you compare an A8 to an i3 the A8 comes off worse (more cores) at load. however, whether this translates into a meaningful difference under normal usage I do not know - if battery life is 5hrs does 3 or 4 minutes one way or another really matter in the real world
Just to make it clear I am neither an intel nor an AMD fan boy, I will happily use either and have done so in past. I keep meaning to get round to a simple HTPC build and AMD will be my choice (but the Zotac nano AD10 is so cute). Of course as of today the i3 is £10-15 cheaper than the A8 at scan