In the May issue of Poker Pro magazine, Nick Brancato was asked about the differences between cash games and tournaments.
The single biggest difference ... is stack size relative to the blinds. In tournaments, it's typical for the average stack to be 20 or 30 big blinds whereas in a cash game, the average stack size is often 100 big blinds or more. Shorter stacks lead to the chips going in preflop or on the flop rather than on all streets with room to still bet and raise on the river.
Also, you never have to be short-stacked in a cash game because you can reload at any time. Therefore, short stack strategies are not necessary. Yet, they are a critical skill for a winning tournament player. You have to familiar with push-or-fold hand ranges.