Interesting comments Jim. I just had my first ride on a new to me Gazelle AB 531c frame yesterday and despite very small tires on the bike, I was impressed by the smoothness. More compliant than my 731os Condor, but likely not as good a climber.
What I did notice was the Gazelle seems a little stiffer than my Trek 760 which is also a 531c frame. Though the Trek is outfitted with modern DA so that may be impacting the degree to which I hammer it.
The Gazelle is surely worthy of a lighter more modern build than I gave it. Oh well, a next winter project already.
Bottom line is that choices are good to have.