I have the 630 and the 730. I'd be hard pressed to choose which one is my favorite. I'll go out on a limb here and say that I think the 630 is the "better" machine. It's performance is nothing short of perfection, whether sewing or embroidering.
The 730 however, has so many features I would just HATE to give up. I love the 16 way directional stitching. For those that quilt, this can be a godsend when you've got the middle of a large quilt bunched up under the throat of the machine. Just choose your direction, and let the machine do the work!
I really enjoy the thread cutter, although I can live without it. And I love the 9mm decorative stitches, I use mine a lot. The 730 is very, very smooth and quiet.
I prefer the embroidery screen on the 630 over the 730's. No, it doesn't have as many features, but I simply love the way it's set up, very intuitive, very crystal clear!
I use both my machines for embroidery and both for quilting.
Have you "Tinkled" today?