Sorry if it is all muddled in my explaination -- the original speaker is an AKCA judge and a very experienced hobbyist. Both parts enter into it -- even AKCA judges will look towards the 'future' of a smaller fish when judging and I think this is one of the things they look for.
The 'rule of thumb' is to pick the color quality based on the quality in the front of the fish for sumi and near the back for hi. For example, a sanke with weak hi on the tail tube is not considered as nice as a sanke with stronger hi on the tail tube but weaker hi in the front. The thought is that the hi will get stronger on one fish while the other probably won't. The best indication of future sumi development is looking at the shoulder for sumi on white background -- if that is strong but the sumi elsewhere on the fish isn't so good then the expectation is that the other sumi will get better.
The rule of thumb does have exceptions, of course. Just like the concept that 'you get what you pay for'.
I still remember the comparison of one of my sanke with another hobbyist's sanke at a young koi show. The head judge (a different judge than the above) was talking about both fish as a lesson for the assembled gaggle of hobbyists. The confirmation on my fish was better, the sumi was up but not good quality and the skin was fine. The other fish had better sumi on the shoulder (very nice), better pattern, better color quality overall. But the other fish didn't have finished sumi overall; even some on the tail wasn't really finished. The junior judge said that confirmation should tip the balance, but the head judge pointed out that overall quality should tip the balance.
I think the head judge is/was correct. The other fish was better and much more tategoi. Part of the reason for that assessment is that sumi on the shoulder -- it shows a better future for the fish than hoping for the sumi on the tail to solidify as well on the shoulder; it is already there.
Oh, and part of the reason I think the judge was correct -- the other fish cost 10x as much as mine did.
