One other factor to consider when choosing between B-10/B-15(A) repros that might not matter to a lot of people is the throat latch. On my original B-15A, it's very easy to close the throat latch and button it up. Same thing with my Buzz B-15. In fact, it's maybe even a bit easier to close than an original. But on Natalie's Eastman B-17, for some reason, the throat latch and buttons are positioned such that you REALLY need to struggle to get it to close. It's basically non-functional. For most people that might not matter, but as someone living in the northern midwest, I actually turn the collar up quite a bit, so the throat latch is very useful!
Otherwise, in terms of materials, they're very much equals - Eastman's a bit better on the knits, Buzz is a bit better on the quality of the mouton, and imho they're about equal in terms of the alpaca pile and the shell.