On sheer coolness factor, Optimus Prime wins.
On a more practical level, Liberty Prime is nuked by a missile he knew about half a minute before it hit. If Optimus was given the same warning, there'd be no catching him. Take any clip from the movies, be it the live-action ones or the G1 movie. Either way, he shoots stuff that's moving faster than anything Liberty hits. From this, we can draw that Optimus is much quicker on the draw than Liberty. Optimus would just keep moving, spam lazors, and probably hit Liberty through the eye before too long. Liberty would spam nukes and lazors and stuff, but none of them would hit, he'd be telegraphing his moves like a bad Metroidvania boss.
Liberty Prime was built to fight targets one-tenth his size, and he does his job with bombs and lazors to spare. Optimus is trained to fight giant robots, and he does it extremely well. It's like pitting one soldier with an anti-tank rifle and molotov against a tank with no machine guns. One's job is to take out the other, and the victim is designed for fighting something else.
Varsaavius wrote:As the size of the explosion increases, the amount of social situations it can't resolve approaches zero.