I've done both. Done well with both, did bad with both. My opinion is that judges have an expectation of what they are going to get, if they get something different it better be much better than their expectation or it will score particularly bad. I think the average judge expects to get spares, so if they get BB's they better be amazing. Therefore I've been using spares this year.
What should a smoker of BB's do differently to a rack of spares than they would to a rack of BB's?
I completely disagree with your contention that "judges have an expectation of what they are going to get" when it comes to ribs, except they expect "good" ribs (no matter what kind or cut)!
I've been judging for years and have NEVER heard another judge say anything about rib types or cuts or anything. How good it was, yes, but not about the cut unless it is completely different.
Believe it or not, MOST judges do not go into the judges tent "expecting" something in particular. We judge what is presented.
Not a slam on Judges, just human nature. No matter how much everyone wants to declare that judges are totally unbiased, the reality is that every single person has likes and dislikes and it is impossible to ignor them. It may not be a conscious decision but sub consciously we know what we like and don't like. Again, just my opinion.