I had the nut straight on the flop (second nuts because I had no diamond so there is a very small chance I get freerolled.)

Against strong players leading out is probably best. Against weaker players and a player pool that tends to flat a lot of draws they would otherwise semi-bluff with I like a c/r to set-up a turn push or worse hand (sets, combo draws, maybe two pair, perhaps lots of other stuff for the fish) to "fuck it" shove over.