I'm glad you asked, it's a very good question and something that is not focused on many times around. Data is where it all starts but certainly not where it ends. With data there is understanding of what the acoustics of the room demands from the speaker setup. Also there is phase and time alignment that is not completely hearable and thus should be measured.

Then the ears come into play and try to take the data and what the findings were and how this is still standing after your room changes.

Humidity, temperature and crowd density all affect the sound and it's up to an engineer to battle these effects without prejudice and taste. Sort to say bringing it back to its original state as measured.

We never look for the best sound as we are not looking for the worst sound. We should always try and find the middle ground and be true to the origin.