For gaming, most of the times, not even half of your cores are getting used.
Intel has a better per-core performance, but usually costs more.
For 3D modeling and things like that, I believe that you'll get better performance with that 8 core, than with the 4670k, but not for gaming.
The difference between those two is not really HUGE, but in some CPU intensive games or even zones, your FPS might fluctuate a lot, and drop, where the Intel CPU wouldn't have this issue.