Which mutant to use rank r5 stone?

Naus79_

I'm having a hard time making the decision... All are awakened and i have stones to have a high signature if needed.
Which one would you rank up??

Thanks!

JuggerNot

Don't think you should give them to Prof X as he doesn't really need it (though it is convenient). Unless you use him every day, if not go for Namor because of the niche utility and prestige