It depends. What's your image like at that point? Are you precieved as tight post flop (i.e. only betting out when hitting the flop)? Or have you been caught bluffing recently. Maybe image doesn't matter against this opponent that's not really paying attention...

I think by default HU, I'd bet out to get bets in. Of course, if your opponent is laggy and shoots at the pot a lot, I'd either pop on the river w/ a c/r.

Passive calling station type I'd bet out all the way.