A XC bike typically has less travel (front and back) and a more aggressive geometry (ie more forward leaning). As a roadie this is something you will be fairly used to. Overall these are the faster bikes.
A trail bike has a more relaxed geometry (more upward) and have more travel (rear and front). The bike is designed to handle rougher terrain in a more comfortable manner.
Unless you have the desire to ride things as fast as you can, I would go for a trailbike for the use you mentioned