Carb heat on during the downwind leg until on the deck.
Just have to bear in mind that some engines completely do not like full throttle (especially if applied to swiftly) with the carb heat out. May give rich cut.
However chances of that are less likely (and unless it stops - easier to cure) than icing up when you go to 'cold' on finals.
Depends on what you are happiest with for your particular mount.
Injection takes the guesswork out of the equation.
FD