Who to rank? 5* NC or 4* Iceman?

Dexman1349

Simple question:
5* NC (unduped) to R4
-or-
4* Iceman (unduped) to R5

Iceman fills a good hole in my lineup for immunity on my attack teams (especially for AW & AQ), but NC makes one hell of a good war defender.

I was originally saving for NC, but then pulled Iceman last week. Other notable Mutants in my lineup:
5* Storm (unduped) at R2
5* Blue Cyclops (unduped) at R1
4* Cable
4* Rogue (unduped)
4* Wolverine (unduped)

I don't have any other R4 5* champs in my lineup and have 11 other 4* champs at R5.

Dizzy

Maybe it's because I'm relatively new to the game, but I've been holding onto cats until a really obvious rank-up scenario turns up. I don't have anyone at 5/50 yet, though I could take up my Starky or Void right now - I'm just planning ahead for the future where I need to focus on 5* over 4* to stay relevant.