You raise some good points, the only thing I would say about Unbridled is that he is a very unique sire. This is for a few reason:
1) He foals seem to be either a Grade 1 stakes or bottom level claimers. You either get it all or nothing.
2) Though he is usually a late developing sire, he also gets precocious horses who peak early like Unbridled Song and Anees who both won the BC Juvenile and were non-factors as three year olds.

Basically, Unbridled is like the D. Wayne Lukas of sires. He certainly gets a lot of nice horses, but no one talks about the huge number of bums he gets or the huge ratio of foals that never make it to the track. Also like Wayne, when they get going good, they're tough to beat. So while I use the TG sire numbers a lot, I think Unbridled is an example of a sire whose is so unpredictable that they're not that valuable.

Another factor to consider is that classier sires tend to be bred to classier mares which has two results:
1) Typically owners who have just spent a small fortune buying these well bred horses don't want to see them break down first out and hence, they don't get wound up at quite as young an age
2) Since a majority of the most prestigious races are around two turns, the horses with the classiest pedigrees tend to develop later and have a bit more stamina.

Anyway, all this is a long way of saying that I would rather have a 2yo Unbridled who could run a 7 then a Sea Hero, even ignoring the residual value factor. Whether Santa Catarina is for real is another question. I think I'll play Ionia and Mac Melody and back-up with Santa Catarina but I'm going light in the race. Thanks for your points, it's always nice to have an intelligent, well-thought out discussion on this board.