SS2 vs. SS3? It really is a matter of taste. Both games play pretty well and emulate genre. We just revisited some stuff with 3rd to clean up aspects of play that bugged me.
One major attack, per character, per turn, vs. a single character attacking 2 - 3 times is the biggest difference.
As to the complexity--it's something you'll internalize over time. Also, if you initially avoid power pool and variable-type powers you won't run into a lot of complexity in the builds. One major thing for SS3 is the way Super must be bought to support higher dice totals. If want a 6D or higher pool, that's superhuman and so you need to buy a level of Super (a re-roll for the pool, essentially) for that.
Anyway, glad folks are talking about the game--any edition of the game!

Thanks!