Originally Posted by Blue Order
I am also wondering if the higher profile of the 26" tire creates a tire/wheel diameter that is so close to the 700c tire/wheel diameter as to make the question moot.
Quite the opposite. If the 26" wheel has a fat enough tire to give almost the same wheel diameter as a 700 c wheel, it will likely be far slower. That fat tire can't hold the high pressure a thin tire can, so it will deform more as it runs along the ground and will have a much higher rolling resistance. It will also be a lot heavier.