I think big snails with trapdoors feature in "species mixing disasters" either in the list on caudata culture or in a few threads in this forum. The trapdoor can trap toes and large snails can be a choking hazard.
My axolotls eat planorbis snails, they used to be common in my fish tanks but are rare in the axolotl tanks. I had a juvenile in a tub which grew fast with no other obvious source of nutrient, its droppings disintegrated into piles of bleached snail shells.
I wonder if another juvenile which stopped eating for a very long time was obstructed due to a snail shell. Its symptoms indicated obstruction and its tank was free of gravel but not snails.
On the whole worms are safer. Crushed snails are eaten with relish and may be fine if this is what you plan, but stocking the tank with small snails which if uneaten become large snails is a bit risky.
Also consider if the species is one which will trash your plant decor!