Considering chess is a draw with best play, and theory extends further and further, I would assume 'best' is what gives you better practical winning chances at your level.
I think this is the most important point on the thread. And since the Ruy is one of the most strategically complex, it is one of the 'best' at the top level.
I play enough OTB chess to know that I shouldnt argue with my superiors ( GMs in particular ) as I have had enough beatings by them to understand that they know far more than I do about chess .