I like the 3-bet here.. it gives UTG a chance to call oop with hands you dominate and if he folds you are building a pot against a fish.

Since UTG is likely never 4-betting worse, you can safely fold if he does.

Flatting here is really bad imo.. if the board is low cards and utg barrels.. now what? In a 3-bet pot you can stack off but in an un reraised pot you are in the dark postflop.