The Energon Pub

Optimus will win. although it will be war with magnus.

Optimus, Magnus always consider himself inferior to Prime.

In a straight fight, UM wins: he's bigger and stronger. OP could try transferring his mind to his trailer or Roller in a bid to escape. UM would stop this with a few shots.

Alternatively, OP wins with a shutdown code. He's learnt to expect the unexpected.

OP can also win with an ambush, spraying UM with trailer missiles and powerful, accurate laser fire. Roller could be fitted with a large bomb and used as a kamikaze bomb drone. However, UM is built to survive ambushes. He could find cover or even use a large object as a shield. He can return fire with equally accurate laser beams and missiles.

On balance, I'd say that the shutdown code wins this unless OP is knocked unconscious immediately.