I just purchased a 2020 Grasshopper 729, having just sold my 2000 721. One noticeable difference other than more power and speed is the exhaust noise. On the 729 the exhaust sounds as if you are next to a wall and the exhaust is bouncing off it, that is when you are wide open throttle with the mower engaged and going about half speed. I find it somewhat annoying. My 721 had completely different exhaust noise, both had/have the 3 cylinder Kubota water cooled engine. One difference is the engine and muffler on the 721 was in an open area while the 729 the engine and muffler is in a full enclosure. What have others experienced. One other item, it seems the 729 uses more gas than the 721.