In my experience, there's not much difference between a hybrid bike and a road bike as far as burning calories go. What matters is, how high my heart rate goes and how long I can keep my heart rate elevated. The idea being, you put out the same amount of effort into exercising regardless of the bike you are riding. What ends up happening is, for the same amount of effort, you will end up going faster on your road bike than the hybrid bike. But for the same amount of effort, the amount of calories burned should be the same. If you are doing a relaxing ride on the hybrid bike and going all out when on the road bike, of course the amount of calories burned will not be the same. But the calories are still burning... compared to say... me right now... sitting at the office typing out this reply...