I thought we were talking about certain aspects of a system being objectively better than some other. Imaging in particular being cited.
And I personally believe if 100 people listened to a system and said the singer was center imaged on 1 system and on another system the singer was out both speakers that one is imaging better than the other. This happened at an audio show while Audiophile Junkie was filming. He told the exhibitor the system sounded bad. They called him back later and said something was out of phase. When he listened again, he said it was much better. In this case there is a technical reason to support why the system is viewed as inferior.
For objective proof it has to be measurable and compiling opinions does not meet the requirements as opinions are subjective by definition. A subjective conclusion requires a measurable/quantifiable and repeatable assessment. In The example you made it could be the same system with the speakers just wired out of phase in the second instance.