[Guy McSucker]

I've thought some more about this and the right move seems very clear, but of course it could be that my brain is not working.

If the preflop 3-bettor's range is what I think it is (as baron said, JJ+ and AQ+) then after the flop it's about 50/50 that I'm in front of him:

I beat:

JJ x 3
QQ x 6
KK x 6

I lose to:

AA x 1
AK x 8
AQ x 8

As for the other guys in the pot, anything could happen.

I think it's much easier to judge which side of this I'm on if I bet: if the PFR has me beat, he'll almost surely raise the flop for value, whereas if I am beating him it is very unlikely he'll raise all these players. So the flop action will tell me where I am, and on balance bets going in to this pot are +EV for me, so a bet can't be wrong and it will help me play accurately the rest of the way.

On the other hand a check could be awful since if the PFR bets I won't necessarily know where I am, and if he checks it through then I've given everyone a free card when I almost surely have the best hand.

So on balance I think a bet is the clear winner here. Anyone disagree?

Guy.