Reynolds 953 is a remarkable material. What you are paying for is the ability to make a very strong and fairly stiff frame in steel without much of a weight penalty over carbon/titanium.

I'm no metallurgist. However, I am having a frame built for me at the moment and had a lengthy conversation with the framebuilder about the relative merits of stainless vs reynolds 853 or Columbus Spirit. His opinion was that I as a big rider (6'3", 195lbs) who might be racing the bike would need the oversize tubing in stainless in order to get the stiffness and durability I want. I prefer the aesthetics of the narrower tubes So we went with columbus spirit. Had I been a smaller rider we'd have come to a different conclusion.

It isn't just about cosmetics.