I can't answer what is the difference between them, as I don't have one. But, when I bought my new machine I was going through this same problem. Sewing or sewing/embroidery. I decided on 2 separate units. Embroidery takes a little time to do, so when I do get my embroidery I can be doing 2 things at the same time instead of waiting for it to get done.
I don't know if this helps out any.