I purchased a rubber tracked KX-91 (~ 7200 lbs, 24" bucket ) just for clearing personal land, not for commercial use. I recently fabricated and installed a thumb. I can tell you what I've done with it, but can't compare it to a 580 because I've never operated one, its also smaller than you mentioned, but close. I too have a small TLB, and the mini beats it hands down for any digging job.
Yesterday, I had two piles of 18" to 36" diameter 11' long logs that were sitting on the ground, I wanted to raise them up off the ground to prevent the bottom logs from rotting before I got them to the sawmill. I placed some trash logs along side the piles to stack the lumber logs on. I turned the cab sideways, reached out and grabbed a log, picked it up, keeping the cab sideways scooted the machine to the new pile and set the log down on the the trash logs, I did this for 38 logs. No other machine I know of could have accomplished it so easily. I wish I had some pictures, but was preoccupied. Some of the logs were too heavy for it to lift over the side at full or partial extension, so I had to work them in close where it would lift them.
I can scoot it right up next to a building and dig parallel to the building within a few inches using the boom swing and turning the house.
I haven't dug out many stumps with it, I usually attack the entire tree and use its own weight to being it down. The mini does not have the pushing power of a full size backhoe, so I usually have to dig on all four sides of a large tree - not just three sides - which is a little risky. Yes it will dig out big stumps, but getting them out of the hole could be a challenge.
I can get it in between closely spaced trees, and use the boom swing and turning the house to get at the trees to dig, its very maneuverable in tight spaces and can turn in its own length. Note that the cab sheet metal dents easily. Dragging them out and to the burn pile is another story, a tractor is probably best suited for that. The thumb is a must have for lifting logs to the top of the burn pile so they can dry, pushing up the pile while burning is probably better left to a track loader.
The front blade can do almost anything a full size dozer can do but on a much smaller scale, I've used it to cut drainage swales, scape back mud, and to back fill holes from removing trees. I also always lower it to help stabilize the machine when digging.
Yesterday I was operating in mud to the top of tracks, I was worried but no issues. obviously in the mud it could not push large amounts of mud. I've also operated over stumps and logs, no problems. The trick I learned driving tracked vehicles in the military is that when operating in any rough stuff is to make gradual turns if possible and avoid locking the tracks, the tracks will clear themselves of debris in most cases if they are allow to turn.
It really does not like wet metal ramps with the rubber tracks, the first time I loaded it my trailer in the rain I almost s**t myself because it started sliding sideways off the ramps. I ended up welding metal cleats every 4 inches on the ramps so the tracks would have something to grip.
Travel speed, even in high range its slooooow, not going to win any drag races.
Sorry to be so long winded! A few pictures below, the picture with the log is from last month. The others are after I scrapped off most of the heavy crud this morning-- awaiting pressure washing and servicing...
