The reason why one might not trade Allen for Mahomes is that you should evaluate them as if they had been in the same circumstance (i.e., apples to apples). And for all of Mahomes' success relative to Allen, the argument could be made that M is a huge benefactor of coaching, scheme, etc. As some have said, would Alllen have had similar crazy amounts of success if he had been the Chiefs QB instead of Mahomes? And how would Mahomes have done here instead of Allen? I think the two QBs are both extremely good. It's a close call IMHO.