I agree that we all love the one we have for the most part. I have had 4 different brands of longarms and they all but one served their purpose. I do feel that customer service and local support are largely important. Not just for repairs, but for those little questions that come up. Ease of maintanance is a biggie for me. When I decided to be a dealer, I went with Nolting. I feel that they are the easiest to maintain, have great ease of movement, and the company is the picture of customer service. And for the money, you can get a top of the line system for about 3/4 of what other companies are charging.
The last thing one should consider is resale value. There are several companies in the longarm market that offer their used machines for such a low price to create cash flow that they destroy the resale value for the customers that might want to trade up or have to sell for personal reasons.
All this being said, test drive all of them you have access to and keep good notes about features you like and don't like. Then go back to the two or three that you liked the best and quilt, quilt, quilt! You will know which one is best for you.