I'm a theatre person as well and back in high school you could only do musical or spring sports which sucked for some of the other kids. I think you should at least try to do both and if you just can't do them then choose the one that you feel better equipped in/having the most fun in.
I do Performing Arts in college and we have to choose between different modules. I tried everything for the first 2 months and looked at my strengths, what I liked and what would benefit me more in the future and made my choices from there.
Hope that helps and best of luck in whatever you pursue. :)
Maybe you should try and talk to the teachers about it in case you could do both at the same time but if that doesn't work out then just do what you feel like you want to do the most, it's your choice - I'm sure nobody is holding you down on that. Although, I'm sure that you could do both at the same time because that's what I do with my other stuff so yeah. Good luck :)
I personally would choose theater. In my opinion being on stage is more fun than being in front of a loud group of people. Also, I think the people in theater are generally really nice and funny and just fun to be around. I'm a theater girl all the way haha. But that's just what I think. It's really your decision.