If this is for your 75 then it could benifit from snails and hermits both. Both have a job to do snails will clean the rocks and glass, some the sand, hermits - scarlet hermits will clean the rocks and sand, they can get into places that the snails can not. They are not that distructive and sure has been an asset in my reef.
Check the U-Build it for a list of clean up crews to get an idea on the different snails and hermits. I agree to stay away from the blue leg hermits as they are aggressive little killers.
Thomas