It's been my experience that FIMing and topping produce about the same yield, and FIMing is harder to do properly. FIM is a kind of topping, but the placement and shape of the cut is critical. If you do it right you should get 3-8 new branches instead of 2 or 3 with topping. The more branches, the smaller each cola per branch. It kind of evens out in the end. Now... I'm ready for the insults and disagreements.