With the Ameraucana, I would expect a blue chick, but probably not blue eggs. I'd expect them to be green. Two different things make up egg color. The base color is either white or blue. If you open an egg, remove the membrane, and look att he inside of the egg, it will either be blue or white. Now that white can be different shades. I opened one yesterday that if I had not known better, I would have said it was brown. But there is a gene that produces either white or blue base shell color. There are obviously other genes that determine which shade of blue or white that is. Blue is dominant, so if just one of the pair is blue, the base color will show as blue.
The brown color in eggs comes from a few different genes. That gene combination determines what shade of brown, green, white or blue the egg will be. There are a lot of different shades of brown possible. Think of it this way
Base white + no brown = white egg
Base white + light brown = light brown egg
Base white + dark brown = dark brown egg
Base blue + no brown = blue egg
Base blue + light brown = light green egg
Base blue + dark brown = Dark, maybe olive, green egg
Since the Orpington lays a light brown egg and the Ameraucana should be pure for the blue gene and have no brown, I would expect a light green egg from the Orpington/Ameraucana match.
I get in trouble predicting Splash and Buff a lot. There are a few different ways to make buff and other things can be under these basic colors you are not aware of. You have to make certain assumptions and they can be wrong. You never know for sure what is hidin under there genetically. The way I understand the Coronation, they are basically the same as Light Sussex, except the pattern color is blue.
With any of these, the Black, Coronation, or Buff, I'd expect a blue chick but not be shocked if something else shows up. You n I'm not going to guess on pattern color or even what pattern might show up.
Which rooster should you go with? I'm not exactly sure of your goals. I'm guessing you will not be saving any of his sons for breeding, so that part does not matter. I'd lean toward the one that best suits your goals and go with him. Maybe getting green eggs instead of blue would appeal to you. But that depends on your ultimate goals for these chicks.