YOu burn more calories the heavier you go. I would stay between6-10 reps to get big and to cut up. The heavier you go the harder your body works to lift, so the intensity is higher. There are studies that show you burn more calories lifting heavier and it's also common sense really when you think about it. To burn fat is all about training, diet and cardio. Reduce calories and/or up your cardio. Now ifyour 4-2 weeks out from a contest I'd go lighter and focus on flexing your muscles to make sure you don't get injured. Then I would go with some higher reps. Your energy could be pretty low because of the diet also.