[AndrewJ]

Depends on the hillyness factor. 'Bents are better in the flat stuff because of the better aero. On the hills they suffer because the riders seating arrangement isn't ideal for powering up a hill.
On a "normal" bike the rider can use gravity (their own body weight) to assist them in climbing by standing up on the pedals.

As with everything, what you're dealing with here is tradeoffs. If you're looking to go faster up the hills you'll need something completely different than if you're looking to bomb down the flats faster.