I can tell you who WON'T win...emerald crab.
I just purchased two of them because I saw some bubble algae growing in the tank. No sooner did I put them in...that one starts reaching his claws out for a snail sitting in front of him. I thought "oh no, now all my snails are doomed". But he reached out for the snail...opened his pincers...and promptly picked off a piece of algae from the snail's shell. He must be a little sweetheart. hehe