Okay, I have to chime in here and share my love of my 15-91s. I agree with all that Linda said..... but one of the things I love about my 15-91s is that it is in a cabinet and stays put when I FMQ. I have mine set up next to an old table that supports the quilt while FMQing. That makes such a difference for me. The machine stays put, no moving around, while that huge quilt gets moved back, forth, and around. I just finished a 74x84 quilt without any problems.
I didn't think I wanted another cabinet.... so little room.... but it really does make a huge difference.
And, I've purchased 3 15-91s..... 1 for my summer cabin, 1 for my son's house where we spend our winters, and 1 to give my SIL for a birthday present. She came and FMQed on mine and really wanted one..... so, I had to find another. They ARE great machines.