Well, as far as the "real" grinder go I've only used the KMG, the Bader BII and BIII. To me, the BIII and the KMG are pretty much the same machine. You can get into a KMG for less money (especially if you put your own motor on it), so I think that's been a big selling point for it. Also Rob Frink hangs around here and answers questions which has made them more popular.
The BIII's are used almost exclusively in our guild and folks swear by them. They are a great running, all-in-one package and it runs just a tad more than a KMG. They also have great customer support and will work with any problems. For me, those two machines are a coin toss if you're not strapped to the very last penny.
The Coote comes in at a lower price with fewer options, but I think it's the best budget grinder out there. Some folks will disagree and say the best is the Grizzly because it costs a little less, but the Coote is build like a tank and it has some expansion options that the Griz doesn't have. It's also American made, which may be important for some folks.