Trail bikes are your do everything bike. They're versatile, light, and exceedingly capable, climbing as well as they descend. They're the right bike for anything from a quick stint on the trails to a brutal day of racing.
XC mountain bikes are the lightest on the trail. They give you the ultimate performance edge, so you can go as fast as your legs and heart will allow, and come back grinning. Just point these race-ready bikes in the right direction and go.