Aesthetic is definitely relative. I suppose I should have worded that differently. I was just going with what was already put out there in a previous post.

Rephrased:

For you, and the discipline that you are involved with, what would be a conformational "fault" (not directly related to soundness or useability), that would make you choose to not breed or improve upon it, on an otherwise breeding quality horse?

Your pedigree answer was quite informative. Thank you.

Edited to add: I personally will try to improve on a thick neck or large head, to a point ... If my horse has a large, bordering on jug head I certainly would not want to pick a horse that also had that type of head to breed to. It would be like asking to have a watermelon out on the end of a broom stick. Just an example....