You really can't go wrong with SC2, the V2 version of that tire (the new one) has a very wide temp range on it. That's for the rear. On the front, we've found the SC1 and SC2 can both handle a wide range of temps. The bigger choice on the front is what you prefer for front end feel. SC1 if you like a lot of feedback on trail-braking and don't mind a little squirm under hard braking. SC2 if you like lots of stability on braking. Both have strong edge grip. Personally, I'm an SC1 guy, but we sell twice as many SC2 to SC1 fronts so I'd say I'm in the minority.
The SC3 are gaining steam now with the latest version. The rear is pretty durable, and they're good for cooler temps and don't cold-tear as easily. Outright grip is still below the SC2/SC1 level, so not many guys are racing on those, but for track day use they're becoming more popular due to the lower cost, especially the rears.
