Depending on the game, maybe 2-4 more FPS? Most games rely on the GPU so if the GPU is the same they'll have roughly the same performance. The only exception would be if the game is made by Blizzard, in which it wouldn't be strange to see 5-10 FPS more for going with the i7-4810.
Chances are there is a price gap of around $200 depending on the maker. My personal opinion... not worth the money to get a few extra FPS. Also depending on the game, probably won't even use 50% of the CPU.