jaguarskx :
The Core i7-3610QM is the more powerful CPU by far. There is no contest.
Regarding the integrated graphic core, the Intel HD 4000 is apparently more powerful than AMD's Radeon HD 7640G. According to the following review of the Radeon HD 7640G, the Intel HD 4000 beats the Radeon HD 7640G in 6 out of 9 games.
http://www.notebookcheck.net/AMD-Radeon-HD-7640G.69836.0.html
No where in that review does it lead you to believe that the HD 4000 beat out the 7640g in any games. In fact if you go to the full game list and restrict the cards to just the 7640g and HD 4000 you can clearly see that the 7640g beats it in every game listed.
As for which should you choose, it really just depends. If you are buying a laptop with no dedicated graphics card what so ever, and you want to do some light gaming, then go for the A8-4500m because it's IGP clearly beats the HD 4000. However if gaming is not in the picture or you are looking at playing 4 year old games then go for the i7 because it is far superior to the A8-4500m when it comes to processing power.
Trinity processors will never beat intel processors in raw computing power. Most of the new trinity chips don't even beat the sandy bridge processors in that department either, but if you are looking for a more well rounded set-up then trinity is the way to go. The thermals of the trinity laptops are much better than intel, and they are getting better battery life. The integrated graphics of the trinity is what is making all the difference. AMD got it right, their 7600 series IGP is rocking the HD 4000.