When I was on my Mu P8 w/more upright positioning, and 8spds, I was able to keep up w/full sized road cyclist, but w/effort. When I switched to my Xootr Swift, I immediately noticed the bike, and set up allowed me to again keep up w/full sized bikes, but now with MUCH less effort.

IMHO, I'd say the difference between my Mu & Swift, that made the Swift more effecient was:
- Less rolling resistince w/Durano's, compared to the wider Marathon's on the Mu.
- More gearing on the Swift to find that perfect gear/cadence. (20spd vs's 8spd)
- More foward/less drag riding position on the Swift, compared to the upright, 'draggy' Mu.
- Just my opinion, but I also felt it much easier to get a more powerful pedal-stroke on the Swift.

I don't own a full size road bike, but last week I borrowed a friends full size bike w/the same exact gearing as my Swift, both front & rear. Only differences were the wheel size. (okay...so the wheel size will change the gearing...but both bikes have 53/39 front & 12-25 rear)

We did the same lunch-course that I ride w/my Swift. Granted the 700cc wheels did up the gearing on the full size bike, I didn't feel much 'faster' on it, nor did it make it easier to keep up w/my friend on his full sized bike.

There's alot more to getting an effecient ride that just wheel size.
just my 2yens worth..