Question about working out.?

Me and my cousin are having a discussion about working out. He works out the way a bodybuilder would. He takes supplements, eat a ton of protein, and works out all of his muscles with compound exercises and he isolates all of his muscles. He is about 5'8 or 5'9 and 153 lbs. I am 5'7 1/2 and 127 lbs. We wrestled and he got me to the ground once out of maybe 50 tries and this is while i had a badly rolled ankle from a sports injury. He can curl a little bit more than me and same with ham curl and leg extensions but i am a lot faster. We compare our strength all the time but i like to scale it from him using his strength against me by wrestling me which uses your whole body and it requires speed, balance, endurance, and hand eye coordination while he only compares strength to how much more weight he can lift. we have about the same amount of wrestling experience as each other and i am only one year older than him. I am 15 and he is 14. I tell him that isolating every muscle isn't very good for you and it can't be used practically. I've been told and have read many stories where bodybuilders tear muscles from doing everyday things because they are so used to lifting weights in the same way. He is convinced that because i only do training that is functional like push ups, pull ups, ab workouts, hard interval training as in sprinting jogging sprinting and so on, and hill sprints, and 30 minute runs every day i won't be strong. I workout to become more athletic and better at my sport which is soccer and to also prepare for the military. Which one is more practical to do in your opinion, and explain why.