Hi Greg,
The second one you picked is same one I did. Good choice.. LOL.. There are good and bad with each koi in the pictures, and Showas are among the hardest to pick at this stage. IMO. They change so much. Kohaku is a much easier koi to pick at a young age, as what you see is usually what you get. Many variables with Showa.
Your first pick is a nice koi, no question. But the black is "unfinished" near the tail and finished everywhere else. at least from what I can see. Many think that the sumi (black) in Showa typically finish from tail to nose. Meaning, in this koi, when the tail black is "up", or solid/finished, the other sumi will likely be not as good anymore. The idea being to get all 3 colors all completely "up" at the same time. Can't see that happening with the first koi. Also, the red is not really balanced. it is less in the back 1/3rd of the koi. "Break up" the koi in 3rds and look to try and balance the red pattern 1st. then bet on the black to appear in the areas it needs to in order to complete the picture. Not a perfect simplification, but it is a start.
Hope that helped