My dozer is a 170hp Case and it's pretty good for clearing brush. I ran a 90hp Deere before buying this one and found it to be too small to be productive. It could only handle so much weight before the tracks spun, and it could not turn with a load. It just took forever to do a small area. While mine burns more fuel, it gets so much more done in less time that it's a lot cheaper to do the same amount of land.
Root removal with a dozer is a tricky thing. They just don't pop out. It takes the right angle, and enough of it out of the groud to get enough leverage to push them over. Different types of trees have different root systems making some easier then others to get out. It's time consuming to get a root out, and then to fill in the hole again using a dozer. In my opinion, it's one of the worse machines you can get for tree and root removal.
Pushing brush piles is only as effective as how much dirt you pick up in those piles and how far you have to go. If you can pick it up and carry it, you will burn it cleaner and faster. You also wont have as much dirt/soot/ash to deal with once you are done burning.
The dozer is great for cleaning up and smoothing everything out once it's all cleaned up!!!!
I never use my dozer for land clearing anymore. I've found that my backhoe takes out trees, saplings, brush and debri faster and cleaner then my dozer. I then use my grapple to pick up what I can and carry it to the burn pile. Anything too heavy to pick up, I drag with a chain behind the backhoe. This is more work, but once you've tried to push a full sized tree with a dozer, you'll realize it's not all that bad to hook up a chain and drag a tree with something on wheels.
In hindsite, and knowning what I know now, I would not have bought such a big dozer. I think 100 HP is probably just about right for smoothing and shaping the ground. Being smaller also gives you more visablity and an manuverablity. It would be cheaper to work on and cost less to operate. I don't think that another foot of blade width is all that important in finish work. Especially since you overlap yourself on each pass anyway.
Stick with a name brand and be sure there is a dealer close to you that is good to work with. Be careful of an older machine. Parts can be hard or even impossible to get.
And with any machine, expect to do the work on it yourself. Mechanics are busy and they have accounts already that are their priority. If you need help, they don't have time to come out there.
Good luck,
Eddie