Re: Conn 28M
John G, I wish I had an answer for you. I have both a Conn 28M and a Conn 6M. When I compare them head to head, the 6M has a bigger, fuller sound, especially on the high end. But the 28M has faster keywork and the slick mechanism that can't be beat. Your son is right, it is easier to play than the YAS23.
I don't know why it was never more widely used. Part of the reason may be that everyone was switching to Selmers around the time the Connstellation came out. The other reason may be the brass--I have heard it said that the Connstellation is a "dead" horn, meaning it doesn't vibrate as well. I still don't know exactly what they are referring to, but the brass certainly seems thinner than my other horns. This is all getting really esoteric, however. If your sons likes it, the 28M will serve your son well for years and will sound great in a school concert or jazz band. Plus sax players like me will come up to him when they realize he has such a notable horn!