OK, a physics question for all you science types.
I would argue that a 700c wheel is more efficient than a 26" wheel, because given two cyclists turning their cranks and traveling at the same speed, the 700c wheel travels a farther distance with each revolution of the crank. The extra distance traveled may be small with only one revolution, but eventually, over miles, it would add up. The only way for the cyclist on the 26" wheel to travel the same distance at the same speed would be to pedal at a faster cadence.
So at first glance, it appears that the 700c wheel is the more efficient wheel.
However, I'm wondering about 2 things:
1) Have I neglected to account for wheel and tire diamater? I.e., a 26" tire generally has a higher profile than a 700c tire, so when you factor in the diameter of a 26" tire and wheel compared to a 700c tire and wheel, does that higher profile on the 26" tire compensate for the smaller diameter of the 26" wheel?
2) Is there some extra amount of energy that the cyclist on the 700c wheel is using to turn the crank one revolution due to the greater circumference of the 700c wheel?
One last question... Please try to convert your conclusions into lay English.