The explanation is quite simple, it is whether the robots do follow the rules of logic or rationalizing. By knowing that, it petty much separates the power and any other aspect of various series. That is the difference between what you robot selected. King Gainer from Super Robots, and Nirvash as Real Robots.
For Super robots, can defy logic an always win, unless it is against another one from the type, take a example King Gainer vs Ideon. To set them up against against real robot, is just pathetic, no matter what power-ups, upgrades and so forth it would still be useless. It is like having gaogaigar vs Big O, Gawain of code geass. There is no real fight, just a crushing defeat to the real robots.
As for proof, look at Super Robot War(SRW) and ACE 3 video games,and the sequels of those two. Those games give enough reason why such robots are categorized in the first place. Even mecha anime forums or anime forums in general, and possibly video game ones about them tell why. A forum example is Mechatalk's technology section or others.
It is blatantly obvious which one is superior, without taking sides just because it is a favorite series.
VS
