Flops for 33 are going to be hot or cold, either you hit and you're fist pumping like a champ, or you miss and you fold. (This is if you're playing straightforward obv)

With 56s or whatever, you can hit a lot of flops in a myriad of ways, pairs + FD, pair + GSSD, pair + OESD, two pair, trips, back door draws, etc. You can hit a lot of flops marginally (back door flush draw for example), cbet it, get called then hit an actual FD on the turn, and keep up the aggression. You're not going to be able to fire many double barrels with 33 on QT59 two tone board.