When is the optimal time to use your defensive ult? Against their defensive ults, or wait out for the offensive ults?

In GM/Celestial right now playing Invisible Woman at the moment along with Loki. When is the most optimal time to use your ult as Invisible Woman?

Scenario 1:

Assume it is the 1st point or you are on defense/offense round 1. Both teams all alive.

  1. The enemy team has a few characters, like Storm/Bucky/Starlord, whose ults can be completely negated by Invisible Woman.
  2. You think they have their ults ready to go, so you want to hold onto it until one of them uses it.
  3. Your teammate Cloak/Luna has their ult ready.
  4. Enemy Luna just popped their ult and you know their other support probably has theirs ready as well.

Do you:

A) Tell Luna to pop her ult to force a stalemate

B) Pop yours first and save the Luna ult

C) Try to survive it and hold off, saving 1 or both defensive ults for their offensive ults or to use to push in retaliation?

Scenario 2

Same thing, but only your ult is up and your other support is around 50% or less.