Xenon: Beam Dance or Mecha Purge

For bossing, which is the more optimal skill to use?

EDIT: My brain derped a little bit on the title. When I mean Mecha Purge, I'm referring to Mecha Purge: Snipe.

Snipe for sure, you gain another 30% ignore def and 10% from hypers while using this skill. Note that they are separated lines, so it will not count as 40%. Also, with a lot of bosses casting DR, its a lot easier to avoid it with snipe, along with it beng a ranged skill vs melee. But in terms of damage beam dance is still pretty high. Im sure someone else might prove me wrong on low PDR bosses tho.