Emerald crabs are pretty (if you ever see them) and will help out with general clean-up. Plus, they'll take care of bubble algae.
Personally, I'm a big fan of snails. There are many different varieties, so they don't all have to look the same. And all the ones I have had have been super peaceful and haven't messed with anything.
If I were to do it over again, I would have steered away from hermit crabs. They have killed a bunch of my snails (even though they had a wide selection of shells to choose from), and they climb on some of my corals, which makes the corals mad.