As long as you're playing at 1080p (or possibly at 1440p), either one will be more than sufficient. The i7 is going to be super-expensive compared to the i5, though, but you probably won't notice any performance difference.
More importantly, though, unless you're going to OC the CPU (& especially if you don't have the right chipset to do so), then buying either one is going to be a waste. If you're not going to OC, save some money & get the i5-6600 (non-K version).
As long as you're playing at 1080p (or possibly at 1440p), either one will be more than sufficient. The i7 is going to be super-expensive compared to the i5, though, but you probably won't notice any performance difference.
More importantly, though, unless you're going to OC the CPU (& especially if you don't have the right chipset to do so), then buying either one is going to be a waste. If you're not going to OC, save some money & get the i5-6600 (non-K version).