Sometimes the things people add or take away are not readily visible (audible) to someone that is not involved directly. That being said, it would be impossible to be sure what Kevin Shirley added to the production, the band, the sound, the networking (personally with Joe), the insight, the imagination, or the inspiration, since Joe had input on all of these things as well. Exceptional artists typically think different than everyone else. Their ideas spring from places that most people can't even imagine. So trying to add logic or rationale to determine the reasons "why" they did something would be a lesson in futility.
In past threads and conversations I've heard people say that this album or that album is their favorite or the best. Because of those type of statements I've tried to figure out which one I like the best as well, and I haven't been able to do it. I like them all, but I like certain songs off of certain albums better than others. So in each album there are groups of songs - the ones I like best (could come from any album), 2nd best, and last. And even those seem to change over time, so I couldn't say that because of a certain factor that album "x" is my favorite (or least favorite), whether or not that factor may be production, band or whatever.
PC
“A friend is someone that will help you move............a TRUE friend will help you move the bodies." -- anon