Have to admit, my SAPs don't really care much for snails, especially not if other foods are available. But they do like small pond snails once in a while. All they do is bite off the foot and leave the shell, so I'm not sure they do much good. Having said that, my specimens get their teeth trimmed once a year, if that. Having a population of Malayan livebearing snails is (in my opinion) the reason for this. The SAPs eat the tiny baby snails rather than the adults, and eat them more as a snack than a meal. But in foraging in the silica sand for them, I think their teeth get worn down.
I'm cautious about trimming the teeth of very small SAPs. These puffers can freak out when stressed or handled too much, and if they throw themselves about, they can bruise themselves on the glass, and this kills one of mine within a day or two, and I've heard of others who have had the same problem. Anyway, I know some people don't approve of Malayan livebearing snails as pufferfish food, but I can't say that I've experienced any problems.
Cheers, Neale