on my mind, that's true everything depends on your stack, but that also depends on other players'attitude. I already seen some table with some agressive players with medium stack !
All depends on the pay-places, for instance, if it is a double or nothing tourney, then, everyone will play slowly, and then you can be agressive sometimes to steal blinds ...
If it's a tourney with for instance 900 players, 90 paid places (50-90 are just a little bit like 0,10 for a freeroll or 1,5~2 buy in amount), then players are globally more agressive and sometimes I feel better being prudent and only play pretty good hands.
It's only my opinion,