Hi there -
I have a Gammill - and I think you will find that most people will tell you that they love what they own. That is great, but it doesn't help you much in terms of comparisons. I believe that Gammill, Nolting, A-1, Ken-Quilt, and the dozens of other mid- and long-arm machines are all very excellent machines. I recommend choosing one that is 1) within your budget, 2) has the largest quilting space available (because it's difficult, for example, to make a 16" feathered wreath in two halves if your quilting space is only 13"), and 3) it helps if you have a dealer near you (or friends) who can help if you run into problems. Most of the brand names have outstanding help desks if you call them concerning issues. Some of them have outstanding on-line help (e.g., Gammill), but even if they don't, there are several Yahoo Groups for longarm quilters. In any case, once you decide on a machine, go for it, practice like crazy on it, and don't get discouraged! I LOVE having a machine, and I only use it for my own quilts (and a few friends who I often owe big favors to!).
Best wishes -