Actually that would be an interesting comparison. Take the same bikes, same riders, same hill, but time them downwhill. How much difference does the bike make to the time? Which bike would be fastest for each rider? There might be problems ensuring a unobstructed run down though. And because descending is as much about psychology as physics or biology, the results would not necessarily be transferable to other riders; a cautious descender might go faster on a bike with good brakes and stable handling even if it was less aero, had more rolling resistance and so on.
Come to that, neither are the climbing results; at national champ level, it seems from their comments that stiffness counts as much as weight. At more modest power outputs, that wouldn't be the case.
