You're absolutely right Cindy. That is exactly how the stores would determine the sex, which is absolutely wrong. When I first started keeping and then raising kribs, I got a male everytime they said it was a female.
A sure fire way to sex them is the dorsal and tail fins.
As for which one to keep, I vote for the picture title Kribensis 1. Or better yet, keep both, locate a female, let her pair up with one and then remove the other male.
, you are pretty much guaranteed a spawing if you let them pair off themselves. Good luck.
I think I might have 2 more females that are growing out right now. If you can't find a female, let me know. I will send you one.