Difference of EVGA SC and FTW versions?

The only versions you want are the EVGA FTW, and the EVGA FTW Signature 2.

The FTW + and FTW le are both basically no better than a stock 670, at which point you're FAR better off going with a different brand who has a different cooler.

The only point of going with EVGA is 1) for the warranty, and 2) because they do make the best reference cards. (But non-reference, if you don't need a blower design, is still far better.)