My decision was made for me by DH one year when he had an unexpected windfall (in the way of spending money) and we went to Branson, MO on a vacation. On the way there, we drove through the town where Gammill is located. I screamed, Stop, and I think his heart nearly did. There was GAMMILL all over the outside walls of that building right beside the highway. I already owned an old LA on a 10 ft frame, so was familiar with all the aspects of machine quilting. Those people showed us all over the plant so graciously that my mind was made up then and there. I had to have one. But we had to go through the buying from a dealer thing so that I would have proper service, etc. I got mine for Christmas in 2009 and haven't looked back.
It has definitely been a learning curve for me. In fact, my son did all the learning on that machine, and now does most of my LA quilting--we do occasionally do quilting for pay. But I have learned the loading aspect, tension problems and how to work them out, and am beginning to do my own quilting. Our personal favorite is meandering and free movement as opposed to panto (even though I do have about 20 designs). Mine is a Gammill Classic 26", and I can quilt anything up to 120" easily. We are still working on the bobbins question though (how many bobbins should I fill) so we don't have to quit and fill a bobbin in the middle of the last line of quilting....
I am sorry I can't help you at all with the sit-down method. I have never tried it, and don't feel inclined to even try it. Seems like too much effort to me, even though I do have to do a lot of walking when I am quilting a big quilt. I just make sure I have enough time to spread it out over a three or four day effort. But the Gammill WAS expensive; cost more than our first home on the VA mortgage plan.....
Good luck, and I'll be watching to see what you decide.