People say that the lighter the board the easier it is to flip while others think having it a bit heavier = easier to control.
Guys like Daewon Song or Rodney mullen will ride smaller and lighter but you have to think about it, these guys don't do heavy impact skating. They are all about finesse. Also, they're older and more nimble now. I think if a board is heavier, that makes it easier to suck to your feet when you pop which is why most people who skate stairs skate big and heavy setups. It also helps with the strength of their setup, they'd be less likely to break.
I've also noticed that lighter trucks on mellow boards are harder to flip, unless you're extremely light footed. I think this is because the weight gives you response on your flick. Whereas if a light truck were on a steeper deck the steepness helps give you that response. Of course deck width can play a role in the weight as well and you can play around with balancing it out that way.
I always say its all about balance but with this one I think it really is all about preference.