What characteristics are the least subjective?

[Thomas]

Depends on the level of experience and training, not to mention personal bias.

With perceptions trained people SHOULD agree more than untrained people. Experienced people MIGHT agree more than inexperienced people.

As you said earlier, this is not a simple subject, but it is an interesting one.

I teach wine component classes. I am frequently amazed at how many people simply cannot perceive what seems obvious--but
it happens all the time.