For varsity track sprinters what fitness program should I do? P90x or Insanity?

I'm pretty lean. I don't have a six pack and I'm not "big." But I am in better shape than almost everyone in my sophomore class in high school. My best bet was for P90x since for sprinters in the OFF SEASON you want to do some intense cardio but at the same time do a lot of muscle building which will continuously burn the fat and strengthen muscles. Insanity is all cardio max interval high intensity training. No weights. So am I right? I'm not trying to act like an expert because I'm not but I do really want to look good and be a great sprinter for my school.