I personally would not recommend adding snails to a planted tank .... once they start multiplying .... they become a real menace
Personally- I see snails as an inevitable occurance in a planted tank- unless you have fish that eat them.
I'd rather get a colony of MTS going strong than have the niche open and available for bladder snails.
Most snails, except ones that eat plants in abundance, are going to help out in many ways- cleaning excess food and algae- some better than others... MTS also help by stirring sand.
If there is not an excess of food in your tank you won't get an excess of snails.
Either way though- no matter how vigilent you are- snails of some kind will eventually find their way into a planted tank.