Originally Posted by chinitonorte
Easy, less rolling resistance and weight. You sacrifice longevity and durability. Depends on where and how you ride I guess. I've been rolling 700x32 around here, never get a flat, don't worry about rough roads, and can even pass on the dirt shoulder if necessary.
Lower rolling resistance only on super smooth roads with higher tire pressures. On rough roads, rolling resistance can be much higher than with fatter tires since you will be bouncing around a lot more.