For the most part, no difference. The GPU is going to make 95% of the difference, unless the CPU is so weak that it bottlenecks the system, and neither the 4790k nor the 4930k will be a bottleneck. There are a few games that are heavily CPU bound, but even in those games the difference will be small and the 4790k will almost certainly win due to higher clock speed. Since the 4790k will be significantly cheaper than the 4930k, you should get that.
For anyone stumbling across this in the future, this is not true; for large well developed titles that are well optimized the GPU is certainly very important but there are many games even such as League of Legends, Counterstrike, and others that are still heavily dependent on CPU utilization for rendering.
Saying a GPU makes 95% of the difference, or has that much of an impact on rendering for the majority of games is just un-true especially for newer or developing titles if you're someone who likes to play beta's/alpha's like Hero's of the Storm and or other 'online' based games rather than games developed by companies like Ubisoft and Activision.
When you're building a PC consider the type of games you are likely to play, older lesser supported games are lesser developed to utilize multi core and multi thread CPU's, the same goes for games with smaller dev teams as the focus may be in other areas however also less likely to be optimized for newer more powerful video processors with larger amounts of VRAM.
So..
For instance, you could use an overclocked Q6700 and a GTX 750ti and play League of Legends with no issues at standard resolutions at max settings; however if you played CS:GO you'd see benefit from a multi core/threaded CPU (like an 8350 or a 4770 as the texture packs aren't very large and the game is designed around a large amount of wire frame.
Riot games new 'design' for summoners rift is an attempt to reduce polygonal structure and rely more on artistic effect and larger more detailed textures to better utilize VRAM and have a lesser demand processing power.
Anyway.. yea please just do your research before you pump out a ton of money for things you don't really need, look for posts from people who are willing to go into depth about what they are talking about rather than just making up some random arbitrary number for something completely relative.