I do not know where you got that info from, but they are not realy comparible. Depending on the rest of the laptops specs the A8-3500m is a much better choise.
The I3 is much faster per core but is only a duel with 2 threads whereass teh A8 is a full fledged quad core.
Also the A8 has built in Graphics card thats actually worth something. NOT Intel HD junk.
If you are looking at pure CPU performance, then go for I3, if you looking for more of a balance with the option to game, take the AMD.
They are not really comparible in such a way as they are for different purposes.
And no and yes that AMD 'that' behind.
In the High Performance(500$ and up market) AMDs performance is horrid, but they are still a viable choice for many situations.