Bhanes,
I was told that the difference between the way a vertical bobbin machine and drop-in bobbin machine works, is that the drop-in style has an extra bend that the top thread takes and the vertical bobbin style is much straighter.
I have older Berninas, Pfaffs and Singer with the vertical bobbin for FMQ, it just seems to work best for me. I have been FMQ since 1993, I have some machines that are drop-in and don't seem to have much success. The one exception is my Pfaff Quilt Expression 4.2(sorry its a modern plastic wonder), most of my quilting is done with this machine.
Sharon in Texas