Tire volume and outer diameter are different things. I have to take some measurements to do the math for the volume of an approximately torical space for the two setups.
Various applications of the words “quicker” and “heavier”.
Quicker as in higher speed, or quicker as in more responsive - responding faster to rider input.
Heavier as in more dead weight, or heavier in the sense of more rotational inertia.
The 26 tyre will be around 8% heavier in dead weight terms (all other things being equal). The rim will also be about 8% heavier.
But the weight of the tyre is about 8% further from the centre of the hub. Put crudely, that makes the rotatinal inertia about 1.08 x 1.08 = 1.16 as much which is alomost a sixth as much again.
So the bigger wheel accelerates more sluggishly, and brakes less eagerly. That’s why Cokeurs (and Cokeuses) find that a lighter inner tube alone is enough to make a significant difference: the weight and the radius are both factors.
On the flat at constant speed, the effect of the bigger wheel (26 rather than 24) will be to make the speed only 8% higher at a given rpm. On a ride where there is a lot of acceleration and deceleration (including climbing and descending under control) the effect will be more noticeable.
That all makes sense Mike. Fair enough. I said I was over-simplifying things :o
But more rotational inertia should make the ride smoother and therefore easier to maintain high rpm…
OK, I’ll give up now. I like my 26 anyway 
Rob
That is perfectly true at a steady speed on flat or only slightly uneven ground. 
That’s why the bog standard Coker is so easy to ride, but the Road Razor requires concentration. 
(Road Razor: the skinny 700c)