Have you seen what 57 stone does to an ASV track system? They are classified as Multi-terrain loaders. Sand, Dirt, and Street, Yes they are great machines. But as far as tracked machines go they will not handle the abuse that a bobcat or NH willl. I have seen it, done it. Whenever they are in rocks and you turn, it collects them up and chips away at the rubber coated rollers. While these are great machines for grading and such, They just are not as tough. And as most of us in here know, Tree guys are notoriously rough on equipment. Everything we own is continuously pushed to the limit. Overloaded S/A dump trucks, daily. Chippers constantly eating their max. Skid steers being used like full on skidders and wheel loaders. It is what we do. I used to work for a concrete company, they had two CAT 257s, when it came time to buy another machine. It was a tracked John Deere. The year prior to that, they spent $9000 or track rehab on a CAT machine with 500 hrs, Yet the John Deere has had no problems to date and is beyond that mark buy far.