Just to add another perspective - I love standing to climb and will stand at the drop of a hat. My legs burn a lot more if I sit all the time, it feels as if I really need that change in position. I've read too that standing uses more energy, but to me it really doesn't feel that way. I think people just are built differently, with a preference to the one or the other. But when I stand, I really stand, punching out each pedal stroke, no hovering, and try to straighten my legs completely every now and then to stretch out the kinks.