Originally Posted by terrymorse
"at any given cadence" ... there's the rub. Your heart's the limiter of power, not leg strength or torque. If your heart can't supply the oxygen to the muscles, you can't maintain the cadence.
If you're at the limit aerobically, a longer crank won't let you produce any more power. Only more torque, but that's usually a good thing when climbing. More torque means a lower peak quad muscle output, reducing fatigue.
It is only "a rub" if you limit your perspective to thinking of power in terms of your aerobic threshold... which is to deny a basic tenent of physics that is...power is proportionate to torque be it aerobic or anaerobic.
For those that want to understand the relationship between power and torque more fully which is pretty straight forward, here is a good article:
http://users.frii.com/katana/biketext.html
George