Superman Vs Martian Manhunter
1. Superman has MMs power set, not his own. Only experience he has is (besides using his own all his life) what he knows from fighting beside MM and fighting foes with like powers.
2. Martian Manhunter has Supes' power set, not his own. Only experience he has is (besides using his own all his life) what he knows from fighting beside Supes and fighting foes with like powers.
Pre DCnu versions. No prep. No BFR. Midtown Manhattan. Start distance 1 city block.
EDIT
In the above scenarios, they are in equal bodies. Supes has MM powers. So does MM.
MM with Supes powers. So does Supes.