Not trying to stir things up but, I personally choose the blue legs over any hermit. I have some that maybe go 3/4 of an inch, however have never had a problem with them killing my snails, just make sure they have many new shells of various sizes and styles to choose from, and well fed. (the scavengers in my tank are always fat!)
If I had a quarter for every frag that my turbos knocked down I would have a second reef tank. Glue, epoxy, wedgeing it in between 2 rocks plus glue and epoxy, it doesn't matter, they are bulldozers. The only way I have found to reduce the amount of frags they knock down by half, is when one of my two turbos died.
+1 on the brittle and serpent stars, great clean up, and have only heard of the green serpent stars becoming fish hunters.
just my quick .02
thanks