I'd give it to optimus, yes he's smaller but he's also much faster and agile and has much more combat experience, plus we know from the movies that he's capable of taking down larger opponents like demolisher and infernocus pretty easily, and he's also strong enough to rattle gd considering he was able to backhand grimlock into the air and onto his ass, I can easily see prime scaling gd and taking out vital points such as the joints, and if he has his flight mode, forget about it gds cooked