Saddle bronc, bareback, or bull ridin'?

Ok, so I am getting into bull riding and I am not sure if I should ride broncs or bulls, I'm 15 only 115 pounds real skinny, I'm lanky tho like I just have real lOng legs and long arms. Ohh and I'm not to tall yet I'm only 5'9 but I am supposed to get taller. I am told I have Lane Frosts build and his smile too haha. Oh and idk if this will help but I wear a size 28x32 or 28x34 size pants.