Well I bought a pound of natural hog-casings that are salted down like cod but on these hollow plastic strips. One of these strips will probably do 15-20 pounds of sausage.
I think natural casings are preferable due to the crunch/snap and digestibility. They also take on smoke more readily than synthetic. When fermenting I think ultimately natural is the way to go. But for an intro basic unfermented summer sausage a synthetic casing probably will do for now. Mine will have cheddar and jalapeño...
Do the plastic strips go all the way down the inside of the casing? For the first time sausage making that I just did, I bought natural hog casings. I got them from a farmers market by me and were similar to the these but without the plastic strips. They were all balled up together and I had to untangle them. I rinsed them with water and ran water through them and they slid pretty easily on the attachement.
From my extremely limited knowledge on the subject, hog casings are easier to work with than other natural casings. For me, who tends to be more destructive than not, they worked well. As far as stuffing goes, I was worried that it would come out too fast and I wouldnt be able to keep up. The grinder I have moves the meat out slowly and I have to push it out to move it faster. I would slide the casing off the tube as I needed more. It worked well for me since I was doing it by myself.