I have the HQSweet16 sitdown and love it. My table is 3x3 and then my sewing table (old kitchen table at the same height that holds my domestic) is to the left of it with all sorts of stuff on it. I done everything up to a king-sized on it and LOVE it and have no issues with quilt size. Sometimes I just have a desk chair I put on the right side to hold some weight, but usually I can turn the quilt so the bulk is to the left.
That said, I tend to love to move the fabric anyway I want to go and was already using my domestic to FMQ so there was no learning curve. My mind can't wrap itself around only being able to work in a specific rectangle and then having to roll and quilt and roll again. Just not sure how I would be able to do some of the designs that I like to do! My friend also bought this same machine at the Houston IQF a few years before I got mine.
Not everyone loves long arms and frames and moving the machine. But it is my understanding at least with the HQ16 that you could later upgrade to use it on a frame if you wanted.