Obviously a lot of factors as many others said, but just to eliminate most of them I'd personally focus on stack size, position, and tendencies of your opponents. IMO, with a lot of chips you're most likely going to have the bully persona (at least to other players), so a nice raise would certainly put you in a good spot with such a big PP. However, assuming you have an average sized stack, it's necessary to understand how your opponents play and where they sit in relation to you. If you are facing a limp from a loose call station, then I'd up the ante and see how the flop turns out knowing that they most likely won't bet and you can shut down if the flop is something like AK10. If, however, you are playing a tight player who raised from EP, then even on the button you're going to want to just call because of the strength this person is clearly showing. The benefit of position clearly shows itself in this third example: if facing a large raise or reraise from the mega-tight button in EP, it may be necessary to fold Qs: you always want to have the ability to see how your opponent opens. In conclusion, use pre-determined factors to make the (hopefully right) judgment call, but where everything really matters is after the flop comes out. Just make sure not to get too close to those big cards, and remember you can't always win them all, so if you get a bad beat just pick yourself up, dust yourself off, say good game and close the window.