I have had many types of snails over the years and currently have several types breeding in my tank. First thing I recommend is to not get hermits with snails. Even if you give them empty shells to use one will eventually decide on THAT shell your snail is in.
Different snails do different things. Ceriths are great for the sand but they go all over the tank too. The dwarf ceriths are tiny and don't eat alot so don't be afraid to get a LOT of them. Caribbean ceriths are still a little smaller than most other snails but their shells do add an interesting shape to the mix. Florida ceriths are the largest I have found and having all 3 sizes creates size diversity. Ceriths eat diatoms, cyanobacteria, film, and hair algae.
Trochus tend to go back and forth between the glass and rocks. They are work horses when it comes to eating. There are a few color/patterns available. They also have tentacles all around their bodies which I think is cool looking. They eat the same stuff ceriths do.
Nerites come in a wide variety of color patterns including, grey, tan, red, yellow, and green. They usually stay on the glass. These guys seem to prefer film type algae.
Astreas come with cone shaped or ninja star shaped shells. They can't turn themselves right side up if they flip so you'll have to help or they will die. I only ever had to flip mine once though over a year and a half. Their feeding habits are just like trochus.
Gold ring cowries are really crazy looking and go all over too. They are nocturnal, like most ceriths, and will hide in their shells during the day usually in a shady spot. The shells are bright and beautiful. When they come out at night their mantle wraps around their shell so it can't be seen. Their flesh is grey which isn't very attractive sounding but it has an unusual texture that is sure to keep your attention anyway. They will eat just about anything short if dinos and macros. Especially if they can hide in it.