Some of the gas-pipe frames that I've tested thoroughly have really good geometry for most of the varied riding conditions that I take on.

Gas-pipe frames tend toward slacker angles, which then has me looking for bigger frame sizes which can allow for a sufficiently aggressive stance (getting bars and saddle more foreward of the pedals).
My good gas-pipe bikes look crazily big for my 5'9" but fit well and are comfortable for all kinds of fast riding.

Gas-pipe frame's tubing is stiffer, I agree, so the steering usually feels more solid.
But I wouldn't argue for the point about the un-sprung weight being comparatively lower, since most of the "spring" (flex) action is in the rider's contact points and body, not in the bike's frame!
My observation is that the heavier frames/bikes jostle more forcefully over bumps taken at higher speeds because the extra mass gets accelerated off of the ground with the rider's weight less able to keep the mass and tires in continuous contact with the road.

Note that the '79 (dark blue) Peugeot UO9 Super Sport is the only one of these with a steep seat tube angle, and thus I didn't need such a large frame size to fit me. The others each lose a couple of cm in "effective foreward reach" to their more layed-back seat tube angles, so I needed larger frame sizes for high-intensity riding.




Frame-------------------Seattube Angle------Headtube Angle

White UO8-------------------72---------------------73

Dk Blu UO9------------------74.5-------------------72

Silver Nishiki-----------------72---------------------72

Blue Steyr Clubman---------71---------------------71