I was wondering if I should get the Intel Core i7-3930K (12M Cache, up to 3.80 GHz) , the Intel Core i7-3770K (8M Cache, up to 3.90 GHz) or the AMD FX 8150 (8M Cache, up to 4.2 GHz). I know the AMD is the fastest but what impact does cache size have? Preferably I would like a choice between the Intels as they are less expensive.
Hmm no this isnt true, Bulldozers are great they just slacked and still havent updated windows to work with all 8 cores after 10 years of waiting its annoying yes but meh, the Fx also has the guiness world record for Speed and performance
It depends on what you are doing with your computer.
For gaming: i7-3930K
Most games are only able to use 2 cores, the i7's power is split between 6 cores and the AMD's between 8 cores. That means more power per core in the i7.
The only engine i think is capable of using more than 2 cores is the Frostbite 3 engine, and no major game has been released with that engine yet.