Uphills and downhills vs a flat I started the debate with my brother asking him, "If you had to do a 20km ride around a circle I.e at the end of your ride you arrive at the same place you started, would you rather cycle on a flat or have uphills and downhills to get the best time?" To this he answered "I would rather cycle on uphills and downhills, mainly because I have time to recover on the downhills." I said that I'd rather go on a flat because you burn out faster on the uphill than you recover on the downhill since the time spent going down is considerably shorter. Id like to hear from the community on which side of the debate they stand and why.

Note: someone please edit my tags I have no idea which to use.
This question explains that if you travel on uneven ground, your average speed drops. This is because you spend more time in the slow climbs and less time in the fast descents.