The engine does make a difference. In Florida's humidity, a 150 is almost guaranteed to generate ice on descent with no CH. As others have said, I was taught in the Warrior to just give it a quick blast on downwind.
I personally leave CH on until about 100ft agl. You don't want the carb too hot in case you need full throttle a few seconds later. (Or would the extra fuel chucked into the carb just soak up the excess heat anyway?)