Hi and welcome to WTF! You're very considerate to take the time to join here and ask about buying your hubby a nice watch for his birthday.:thumbup1:
As to your questions, the short answer is get the new Seamaster. The reason why I say that is you seem to be looking to commemorate the occasion and a new Seamaster will have a bit of heirloom quality about it since they are desirable. The same can't be said of the Seamasters from his birth year. While not bad, they certainly weren't considered to be the top. The Seamaster of the '50s and '60s on the other hand were considered the pinnacle for Omega.
Best of luck and let us know how it turns out.:thumbup: