really the only difference is the size. Some people claim that blue legs are more notorious for eating your snails, but IMO, the reds are just as dangerous if you dont have enough shells for them to grow into. the reds also get a little bigger.
for snails, there are many different types such as nassarius, cierth, (those two dig in the sand bed), and then there are the normal glass and rock cleaners such as astrea, mexican turbo, and margarita. they very in size with margarita being the smallest and the mexican turbos being the largest most of the time. They are very fast cleaners but can be knocked over in the sand bed a lot and die.