I use soft paws on my cats and I really like them. They will definitely stay on in the snow. They use super glue to glue them on so they'll stay on for a long time. You do have to make sure the glue is dry before you let the pet out of your sight, though. The first time I put them on Misty Blue, I didn't do this and she chewed them off right away.
Usually the nails grow out and the caps fall off or get chewed off when they become annoying to the pet. However, this last time, I had to cut one off because the nail grew out so much the nail cap almost touching the pad of the paw.
I think if you use them on dogs, though, you wouldn't get this problem as much because the dog's nails are thicker and i would think the caps would fall off easier. Do they even make them big enough for dogs?