More threads in a cpu translate to less than 5% performance difference (if that - I was being generous).
The i5 2450m on the other hand is a more powerful CPU than A6-4400M.
The HD3000 on the other hand is a lot less powerful than 7520G.
Also, the A6 should be overclockable. In that regard, you could do the same thing Xenturion did (undervolt and Overclock at the same time and your cpu will not only run faster, but consume less power in the process).
Or, you could ultimately keep the voltage as is and overclock it more (I wouldn't worry about temperatures though as the A6 is a pretty cool chip as is).
I think its possible for an A6 to approach the i5 2450m in terms of raw CPU performance through overclocking - needs to be close to 2.3 or 2.4GhZ though (or 2.6GhZ) if I'm not mistaken.
If you will be using the laptop for CPU based tasks (CAD work, etc.), then the i5 would be a better option, however if gaming is your priority, then AMD definitely (which you can easily overclock on the CPU part and approach i5 in terms of raw performance).