It is considered by some the most difficult winter Olympic sport. It would be my choice. 
It is the diffrence of two extremes thats for sure.
One min you have to have your heart pumping at 100% going full out, the next you need to slow your heart rate, and control your breathing to get a clean trigger pull.
its one of the few sports that no one gets into to do biathlon, they are either shooters that learn how to ski or skiers that learn how to shoot.