I agree with 2 aforementioned points.
1. Try them all. I went to a large quilt show that had most machines. I tried them all the first day and then again the second day. I stood around and listened to people who were asking questions and then found some who had those machines that I was viewing and asked them all kinds of questions. I questioned the dealers about their frames that come with the machines and shook each frame hard. I bought a Baby lock Crown Jewel (18 inch throat) with a Grace Majestic 10 foot frame and have had no problems with them. I love using them.
2. I would ask about dealers in my area. I live on the Eastern Shore of the Chesapeake Bay in Maryland. There are not many dealers around me and none within 50 miles that sell Longarms. Baby Lock had one near Baltimore and another in Croften. I called them and they were very helpful. So far I have not had to take my Crown Jewel to anyone, but I feel confident about my dealer.
Another point that I would mention is classes. Baby Lock offered a 4 day class in St. Louis and because the teacher of that class was at the show, I had the class included in the deal. I think it was special on that day. I learned so much at that class and felt so confident when I got home. But I practiced alot before doing a quilt.
Best of luck to you. I know you will really enjoy whatever brand or size that you get.