I have the 3720 and it is my right arm. I use it on my property and to do landscape and pool backfills. I was in your shoes a year ago and if I was going to go with that size frame of tractor, I went with the largest engine I could fit in it. Plus the 3520 and the 3720 are turbo models. Go to the John Deere thread and you will be able to gain more info on your machine choice.