Go for the i5 4670k. The difference is that the i7 uses hyperthreading, a feature not supported by most games being released nowadays (just a few are). For around $100 less the i5 4670k will provide maybe 1%-5% less performance, and you'd notice no difference in almost any game.
However, if you are not STRICTLY gaming, then you may want to consider the i7 if you are into video editing or multitasking.