The Super Clocked versions guarantee a certain overclock. It does give you a bit more performance (and the cost difference in Canada is like $10, so negligible).
Some people like the SC versions because they don't know how to/want to overclock themselves. If you are intending on overclocking anyways, then you're good with either. I bought 2 SC versions because I got a good price on them.
For clock speed comparison, when looking at EVGA's info:
Core: 980MHz base/1033MHz boost
Core: 1072MHz base/1137MHz boost
So what they're saying is with the SC version you get at least 9% higher base clock rate. In real life though I got the following:
760 SC #1
Core: 1071MHz base/1202MHz boost
760 SC #2
Core: 1071MHz base/1215MHz boost
Memory: 6008 MHz
Then of course you can push them further. Mine at sitting at +60MHz core/+375MHz memory (750 effective) with more room to go.