I'm training an Abomasnow like this.

Abomasnow @ Leftovers
Adamant Snow Warning
252 HP, 252 A, 6 D
Seed Bomb
Swords Dance
Earthquake
Ice Shard/Avalanche

He's my lead for my hail team. With his bulk, he should be able to pull off 2-3 Swords Dances. The problem with Avalanche is Abomasnow's low speed means that it will be usually going last. Its power will be x2, but after 2 swords dances it may be knocked out before doing damage on the 3rd turn.

With Ice Shard, he can do what Arceus does in Ubers. He can sweep, but the move will do 3 times less damage than Avalanche. Also, a common lead is Azelf, which sometimes carries Flamethrower. Abomasnow would take x4 damage. But with Ice Shard, it would outrun Azelf. I was thinking about using both, but I would lose Earthquake, which I need to take out Metagross, another common lead. So, what do I pick?

Firstly, never assume you can get up more than one SD (or any stat) boost unless the poke is a grand wall or has sleep/encore/sub to set up on.

Ice shard is the superior move, you already have EQ and seed bomb for power. So getting speed priority is a great benefit, not to mention hail will kill sashes while you set up a SD, which may allow ice shard to KO some frailer leads. If you further want to empower ice shard use a LO(recoil sucks with this set though) or a nevermeltice over leftovers.

Being a lead, abamasnow will rarely get a SE on his STABs, so EQ is a good move to have. Ice shard gives him a a moderate priority attack, and Seed bomb holds good non-recoil power and covers well with ice/ground.

Ok, I'll use Ice Shard.