I love my sitdown, but I have a HQ sweet 16. I pin baste my quilts and have very few problems with moving the fabric/quilt vs the machine. I've now done quite a few king and queen sized on it with little to no issues. Yes, you have to move the large quilt, but I love that I can travel any path that I choose.....
I was used to FMQ-ing on my domestic, so there was no learning curve. While some hate the sitdown, some love it! Definitely test drive it and test drive the long arms before you decide.