The difficulty with steering the fabric on the DSM was the bulk of the large quilt. If I was doing a very small piece, I could steer the fabric okay. The things I like so much more about the longarm - not having to pin or spray the fabric sandwich. Better visibility of the whole design. With my Innova, the ability to stitch through the heaviest intersections. The machine stitches at a much faster rate than the DSM. I have absolutely no shoulder or back problems from wrestling with a heavy quilt. And in the summer it's so much cooler than sitting at the DSM with mountains of quilt falling onto my lap.
Edited to say that after some practice with rulers I now think that SITD is also easier with the longarm than with the DSM.