Originally Posted by Mitch's mom

15-91 gets my vote. It has a vertical bobbin, huge throat/harp, a gear driven motor - no belts to fool with. Parts are readily available, it uses the big class 15 bobbins and since the bobbin is under the bed of the machine you don't have to remove your work to swap out new bobbin. They are plentiful and inexpensive. I have 3 of them.