Tracks excel in sand/soft conditions, on steep hills, and for tractive effort. Tires excel in grass. Tracks ability to "spread the load" on a loader is wildly oversold/stated. They do fare better in soft conditions, no doubt.
Boxers are excellent machines, but their controls suck moose appendages for a "real" operator. Thomas had (went bankrupt) the best controls of any stand on/ride on mini on the market that I've came across. If I have to replace my Thomas with another ride on mini, it'd be a Boxer. I'd spend the money/effort though and change the controls out. You physically can't do the same things with them unless you have a third arm.
Come to the show in Pittsburgh the second weekend in November and we can chat it up something fierce. I'll spend most of my time in Dave/TNTree's booth as I'm a salesman for him, sorta. We'll have machines there for you to oggle over and pictures/video/literature on several more models.
What kind of terrain will you be operating in? In my area, tires are hands down the way to go for the vast majority of the job. Mountainous terrain or working near the coast (sand) is where tracks have the advantage for residential tree work.
Also, what access width do you need? My machine is 39" wide, and I don't know that has ever made me manually handle a piece of wood.
What kind of budget are you looking at? New or used or it doesn't matter?
For new loaders:
If you don't work on steep ground all the time, you can handle being over 36" by a little bit, and have the budget for it, the Gehl AL140 is phenominal. It's an articulated wheel loader that lifts higher and drives faster than any other mini while doing next to now damage from turning on grass. The controls on it are excellent.
If I had to have tracks, I'd go with the 532 Boxer and change the controls.
If I stayed with wheels, I'd go with the 427W Boxer and change the controls.
Currently Dave's Branch Manger Grapple is hands down the best mini grapple for tree work on the market. Vermeer's is the worst unless someone has came out with better turd that I don't know of.