What is the best decade for quality of multifamily construction

[Serge S.]

I was recently having a debate with my friend @Ben Leybovich regarding the best decade for quality of construction. For these purposes lets disqualify anything 1990+ and limit it to the 50s, 60s, 70s and 80s. Newer is not always automatically better and there will always be varying quality or workmanship.

So ... assuming constant quality of actual construction and buying a 50+ unit apartment complex with NO deferred maintenance (I know its not possible), what would you prefer and why? I definately have my own opinions and I will share those later so as not to influence the debate.