Its a little bit faster stock, and would probably be a bit faster overclocked (the i5s still overclock really well, though, so there may not be much of a difference there either.)
The i7s also have Hyper-threading, so if you use programs that are properly optimized for multiple threads it would have a larger advantage. But, games are mostly not (its more a multimedia editing thing at this point), and the difference between them in gaming isnt really enough to justify the cost.
Heres a comparison for the i5 3570 and the i7 3770 (which is apparently just a little bit more powerful than the 2700) -
http://www.anandtech.com/bench/Product/701?vs=551 Its a bit better than the i5 in encoding, compressing, etc, but the gaming benchmarks aren't leaps and bounds over (for $100 difference).