I found the collagen casings are best for beginners (no matter what equipment you use). The natural casings have to be soaked and handled with extreme care. The collagen casings don’t require soaking and they don’t get all twisted and tangled up. Once you become comfortable with the process, then you can switch to the natural casings.
I have a Kitchen Aid with sausage attachments and a stand-alone meat grinder with sausage attachments, and I have not noticed much difference in the stuffing process. The only thing I prefer grinding the meat with the stand-alone meat grinder. It has a wider opening and it works faster and grinds meat with ease. It also has a metal attachment, which I usually chill for an hour prior to using. This prevents the fat from melting during grinding and stuffing.
Here is a link for sausage casings:
http://www.zachspice.com/shop.php?Call= ... &cat_id=23
Also check : www.northerntools.com
for meat grinders.