from the initial pics I formed the opinion that the kohaku was a male, and the showa was female.
I thought this simply because I could not see a dealer letting that perfectly patterned kohaku go unless he was sure it was a male. And the Showa has enough good points to be a valued fish, but isn't at the pattern level of the kohaku. So the breeder would be willing to part with it before it reached its potential.
And that is how I would have seen it. I can't tell what is going to happen to a koi in the future by looking at it. I can only try and figure out why' it is being sold.
The best way I can think of to buy a koi is to step up to a tank where the fish are all the same price and buy the ugliest ones because the breeder/dealer knows why he priced the ugly one as high as the pretty ones.
"Those aren't poodles. They're Dobermans with afros."