well first of all I think you could alot cheaper on your x99 build. go with a 5820k, and you dont need dominator ram. and your mobo is way overkill. Just my 2 cents. You should be able to get both at almost the same cost. with x99 maybe being abit more.
Not sure why you are spending so much more on the x99 build? you can get a good mobo for under $300.
For pure gaming either will do. I still prefer x99 for the extra cores.