I am a bit familiar with the distress a downguage causes some people on a transcon YVR-YYZ when they thought they were getting a 330 Executive First seat and suddenly they find themselves in a domestic J 767...BUT...

Is there really a difference between domestic J on a 767, 319,or 320. Given the choice would you pick one over another or just go by the best schedule for your needs?

I tried to search...lots of threads...couldn't locate the answer to my specific question...