For a small tractor, there are a lot of good brands out there. I have used and like John Deere, New Holland, and Massey Ferguson. We have an old MF that we use for shredding and driving posts. It is a great little tractor because there's just not much to it. My neighbor has some little NH's and JD's that were great little tractors. Of course, they had a lot of features on them that the old MF doesn't have, but I was impressed with them. They were also 4wd, which was a nice addition.
As far as the tractor, I would seriously look at the closest dealers, whether they have mechanics to work on tractors, and the number of replacement parts they have on hand and the owners personality and devotion. Then I would choose one of them. That way if any thing happens to the tractor, you have a close place to take it too, or buy parts from. Any of the name brands generally are good. I like Fords myself, but that is just what I grew up with. The local Ford dealer in my area will come in during off hours if I need a replacement parts in an emergency.
What Greg said is pretty much what I go by. I have had good dealings in my area with the John Deere and Massey Ferguson folks. One of the major reasons we switched from Case to John Deere for our main tractor was the local dealership. We were having way too many bad experiences with the Case AND the dealership.