Ice Gem should really only be considered if Abomasnow can't run anything else, and I think on any hail team Focus Sash should probably get priority, closely tailed by things like Life Orb. I understand Choice Scarf's usefulness, but I think it's better used on a hail abuser like Glaceon, who has a less diverse movepool. Abomasnow really needs to survive the other members to win weather wars, and being able to use Protect is a big bonus in that direction, not to mention being able to endure one more attack or switch out for later on.
441 D/Cs and counting, baby!
*Contrary to popular belief, this is not a compendium of people who disconnect on Wi-Fi. See: Seinfeld, "The Comeback."