Thank you!
I think I've decided to hold off on any of them for now. I've talked to some members of the local koi club, and then a few people here through PMs. I think my best bet will be to wait until a show to go and pick out a koi in person or wait until I can find a more suitable koi online.
By looking at these and other koi though I am learning to pick out the good traits from the bad, and hopefully someday I can find a koi that will match most of the good traits I like.
Everybody I've talked to seems to confirm that the more I look at koi, the more likely I will be to begin to learn how to distinguish the good and bad traits from each other.
Koi are definitely not as easy to select as shubunkins.
I agree with your comments about the conformation on the Tancho. The Sanke does seem to have the nicest body, but the fins are definitely what I liked (I just couldn't put my finger on it before).
Indeed, discussing and watching are definitely a good way to learn more. Again, thank you for your comments!