I would recommend the Bailey(
http://www.bhqlongarm.com/), I have a few friends that have them and they're all very happy with them. When I have the room and the money, a Bailey is what I'll be getting.
As far as the Mega Quilter, I had the 9" machine and didn't have anything but problems with it, finally said, give me my money back. I don't have any experience with the 18" Mega Quilter but I do agree, 9" isn't much space.