I've not tried copper before myself, though I've heard a lot of mixed reviews about it. I use recycled granite shards, they don't actually hurt the snails and are fine for all other wildlife (including my kids!! ).

There's quite a selection of snail control out there though, I get my shards from he

Slug and Snail Control

They also sell Eraza (as mentioned in a previous post) and a variety of other methods.