I wouldn't even consider clock speed when it comes to buying a card, last time I bought a card I overclocked it before I even launched a game with it. The cooler should be the thing to sway you the most, you can change the clock speed of the card after buying it, but you can't cool it better after buying it.
You get a higher quality GPU by paying more for the SC version. EVGA bins their chips, which means they test each one and only use those that pass a higher level of quality control for the Superclocked and Classified cards. Those chips that do not pass the quality tests go into the less expensive regular cards.
"We sent an email out to EVGA....
What makes your Classified worth the premium being charged if it is now limited to NVIDIA’s (low) Power Target limits with no additional voltage control?