opening a can of worms... anybody want some? :P

I have an exmark 21 with a Honda 5.5 engine. I've owned severeal Hondas with engine from 5hp to 7hp. The exmark cuts rings around the Hondas. It cuts through grass that would bog the Hondas. Any thoughts on why? Seems odd to me since it's just a 5.5 engine.