Get the one that uses teeth and does not require you to change out the entire cutter...(OK, RAYCO) just my .02
What is your budget? I would not get a tiny one, rent one and try it out and make really sure you want to invest in one of those, they can wear you out....maybe look at an Alpine magnum, they can cut much faster and make you more money in the specialized market of hard to get to stumps.