they are both NOT good for gaming, but between the two i would take the A6 3500 because it has 3 cores. Dont be so close-minded, Im sure there are more CPU's to chose from. what are the rest of your system specs? graphics card plays a more important role than cpu, if you have no dedicated graphics card your not going to be playing anything but pre-2003 games. If you can, look at intel cpu's, they make much better cpu's for gaming, even their low end pentium G range is better for gaming that the CPU's you are looking at.
Well if don't mind integrated GPU than the A6 3500 is good enough. It has better integrated GPU than Intel does, but the CPU is a bit less performance than most Intel CPU's. The Ph II x2 560 would be fine with a dedicated GPU (5670/6770) if you budget is tight, but it's up to you.