I'd say that Amuro Rey wins because he became so good that the mobile suit couldn't keep up with him. Any mech that could keep up with him would have to be superior to any veritech fighter in Robotech.
However, the Decepticons are very powerful individually. It is actually difficult, if not impossible, to kill a Decepticon. The Decepticons can use deception to infiltrate the Zentraedi fleet and destroy them from within.
In both the Robotech and Transformers cartoons the enemies (Zentraedi and Decepticons) had displayed a ridiculous amount of stupidity at times.
I'll say that the Decepticons win after a long war. The Decepticons seem to be much better at adapting to new situations whereas the Zentraedi just couldn't cope when faced with a puny micronian force from a species that had never left their own solar system.