if you feel like you play better than the majority of your opponents, more on the table = better for reasons you already know (pay-off with monsters etc etc). short stacks require less skill to play as you can only really afford to get involved with big cards/pairs, hoping to get most of your money in ahead either preflop or on the flop. with deeper stacks you can play more speculative hands (smaller pairs, suited connectors) profitably because they can flop very strong hands or combo draws, and you need enough $$ in your stack to be able to get paid off when they do (thus covering your losses for the times they miss and you're forced to fold)