I have the Australorps, and they are very similar to the straight Orps. I would keep your blue rooster because breeding him to your black hens will give you chicks in both of the colors as for the color genetics of the B/B/S.
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Unless you don't want any blue genetics at all, I would recommend that you decide which rooster to keep based on how closely each one meets the Standard for the Orpington breed. Health, vigor, frame/bone structure, size, posture, growth rate (not too fast or too slow), fleshing out rate, temperament, etc ... are all things that make an Orpington an Orpington, much more so than just color. Compare each cockerel to the "ideal" bird, both the published Standard ideal, and what you want out of your personal breeding flock, before you decide which male will be your best foundation sire.
If you're not sure what all these details mean, you can post pictures of each male and ask people with Orpington knowledge to guide you through the selection process. Post a picture directly from the side, the front, the back, and the top of each one, and be sure to select pictures that represent each male accurately. There's lots of expertise available from BYC members who are willing to help.
Or, if you have the room and like both boys, you can keep them both in separate breeding groups. That would allow you to see who produces the best offspring.
I don't breed Orpingtons, so I'm not going to attempt to evaluate his quality. However, his blue coloration is gorgeous. If you don't hate the blues, then breeding him to a black hen should give you half blues and half blacks. Breeding him to a blue hen should give you 50% blue, 25% black, and 25% splash. So lots of color in those genetics if you decide to go that route. Or if his structural quality is good but you just don't want any color except black, you can still select for only black offspring with good conformation as your primary goal. Lots of ways to use him if you decide he's the better of the two boys.