What is your favorite Lapras moveset?

Fb/Ib for attack
Is/Ib for defence

If I had to pick only one then Is/Ib it is.

Definitely Frost Breath/Ice Beam, but Frost Breath/Blizzard is almost tied with it.

FB/B would be my choice, as I'd prefer Lapras as an attacker. I say that as someone with a high level IS/IB Lapras.

I have IS/IB and IS/B over 2200 and so all I can say is IB > B. And IS is fine to dodge with, but I only dodge charge.
If it's for defence then definitely IS/IB.

If it's double ice, it's solid for either offense or defense. Ice Shard and Frost Breath each have different advantages.

Even though IS does take longer, the bigger hit means you do more damage if you're fighting a bit more conservatively against a really high Dragonite (3300+). It's sometimes a little more risky to double-hit against a really high Dragonite, especially if it's one of those rarer (now) Dragon Claw ones, since those will sneak up on you quickly.

If Dragonite isn't super high, Frost Breath does indeed lead to faster kills though.

Both are really solid, TBH. Ice Beam is more versatile than Blizzard (and less waste if more than one Dragonite in a row). And Ice Shard is more versatile than Frost Breath, despite slightly lower DPS. In the event Lapras gets CP buff, the Ice Shard is also clearly a better defensive move.

All in all, people will have different opinions, but having 84-95%+ of all of these, my play style prefers IS/IB--especially if you're going to spend really scarce Lapras candy upgrading.

IS is legacy, and work well for both defending and attacking, while you are still able to catch/hatch a new one with FB

Attacking: FB/IB
Defending: WG/IB (surprises people)