Originally Posted by
Riveting
Is it the shorter ride with slightly higher avg power, or the longer ride with slightly lower avg power?
That was all wrong. The simple answer is the faster rider will always burn more calories. They both do the same amount of work against gravity and rolling resistance, but the power to overcome aero drag goes up as the cube of the speed while the time goes down linearly with speed. That means that increasing speed always increases the work to overcome drag.
If you're trolling, it's pretty weak. If you're serious, clearly it depends on the length of the climb and the individual's power/duration curve.
Clarification - the difference will depend on the P/D curve. The faster ride will always burn more calories.