There is a huge difference! In tournaments, preflop is the money street. Very rarely is postflop play a huge deciding factor in a tournament. However, cash games are totally different. The turn & river are the money streets. Because everyone is playing with very deep stacks, starting hand values start to normalize (or all become similar). You need to get used to playing with implied odds
being your #1 concern.
And exploiting your opponent's tendancies becomes a lot more important in cash games, since you can choose who you sit with, where you sit, and you can instantly rebuy if you make a mistake.
However, I'd say cash games provide a much more consistent income than playing MTT's or SnG's.