> Depending on your drivetrain, you may find that a stiffer > 5/6-speed chain works a lot better, or a lot worse, than > a narrower chain. Fortunately, chains need replacing often, > so you won't be stuck with a poorly-shifting chain for long.
Exactly!
In my experience, the chain's lateral stiffness is what determines how well it will work with various classic derailleurs. I've found that Campagnolo derailleurs work best with a stiffer chain (you might ask, stiffer than what?), and something like a DuoPar requires a really stiff chain to work properly.
Fred Rednor - Arlington, Virginia (USA)