Best moveset for lapras?

I got these two lapras: 36lvl 91% is/b and 28lvl 91% fb/b
I'm tempted to change blizzard to ice beam in case of better defensive move or dragonite raid boss. Should I go for it? Personally I can't even see blizzard's flash and mostly lucky dodges due an awkward pause in a rythm.
I run some tests with updated SE dmg and it takes 1 blizzard and 2nd is 95% overkill while ice beam takes 2 and 3rd is 95% overkill against maxed out dragonite.