If they're internal, they're probably dissolving kind. That's what they use for ferals, since you really can't bring them back to have stitches removed.
I don't know which is better, though.
I always worry about cats licking the stitches and tugging them apart. I'm going to try to keep my ferals in a puppy crate for a few days, just to be sure nothing comes unraveled before it has a chance to "set up".
When I got two teeth pulled, I had stitches to hold the gums together over the hole. After a few days, the stitches turned white and swelled up a little...they were still kind of stiff. After another few days, the extra parts sticking out broke off. Now I have a nice little seam line right in the middle of my gums! LOL