From what I've heard 'it depends!' - lol...
Assuming 100BB stacks...
-Against very aggressive 3-bettors when you're OOP you really want to be getting as much money in as possible pre-flop, I believe...
-Against players who play predictably post-flop (e.g. high c-bet%, you just KNOW you're going to get extra cash off villain cuz he's going to c-bet whatever comes up, or they play fit or fold and they're nitty) you might want to be calling IP... More inclined to call IP when suited?
-If you're not absolutely comfortable with playing post-flop against a fairly aggressive 3-betty/4-betty type player, then get money in pre-flop.
-Only time I consider folding AK pre-flop: Hero has fairly tight image, 3-bets a nit who is in EP and gets 4-bet. Reason being, the very bottom of nitty villain's 4-bet range is going to be QQ which you're coinflipping with, the rest dominates you apart from having the same hand... Against a real tight nit who doesn't even c-bet light you might want to consider just calling a pre-flop raise as opposed to 3-betting...
Short stacks, get it all in... Deep stacks, be more inclined to see and play the flop...
Think what I said was pretty standard, think this is a pretty well covered spot already... If you read any decent book on beating 6-max it should cover this kind of spot... (Ed Miller's Small Stakes No-Limit Hold'em is a real gem)