The 6600 has a built in walking foot (accu feed system) plus a bunch of decorative stitches and full alphabet in a few styles. No embroidery (other than decorative stitches which, I believe, don't count). It's supposed to be good with free motion quilting but I've never tried it. It has a fairly nice size opening-about 9". Also stop/start button, knee lifter for the presser foot, separate bobbin winder.