And what makes you think Anakin would do better off Mortis against a One?
Or...perhaps I should phrase it another way. How much of Anakin's Full Potential do you think Luke inherited?
Anakin's potential is twice that of the Emperor as of ROTS or ROTJ. It is unlikely they were talking about the Emperor Reborn, who himself is about...what, 120, 130% of his ROTS/ROTJ self? More?