Top Mutant Rank-Up Jamboree

Species11

Which 5 Star mutant should I rank up next? Have a 5 Star R5 Colossus and Magneto. Which would be better for Act 6.3 & 6.4 Completion?

Fear_of_Clowns2099

Apoc r5 is better imo, but do not underrate professor x. Once you get his playstyle he wrecks a ton of stuff. BTW, prof x can bypass grandmaster phase 3.