I bought a new old stock ANSI Model M (1995 manufactured) from Unicomp last year. Beware that they will ship it to you in its original box with no extra padding, so it will likely break rivets in transportation. Expect to do a bolt mod when you get it.
I have two 1989 Model Ms, and the 1995 specimen was definitely inferior. I ended up partially bolt modding it and giving it to my brother. Something about the click of the springs just didn't feel as strong or full as the 1989s. Not really sure how to describe it; it just felt cheaper.
I'm not sure how it would compare to a new Unicomp board. I've typed on two of them: one was absolute garbage, and the other one is pretty decent. I will say that the new old stock Model M will have a sturdier case. The Unicomp cases flip and flop because they have no rigidity.
My two cents.