While the only frame I have any experience with in this class is my Bianchi Proto I am going to say the early '90 class of Columbus Nivachrome tubing like MAX, EL, EL OS, Mini MAX etc and Genuis. I think with the newer material steel was becoming lighter and using differential tubing designs like in the MAX fram and pioneered to an extent in Columbus MS designers and manufacturers the ability to more finely tune ride and performance of the steel frames.

Sadly carbon fiber became cheaper and everyone was convinced they had to have it instead.