Depends what your goals are honestly. If you want to be able to use one of the two in self-defence, do MMA since MMA is Boxing, Wrestling, Submissions. Boxing is one dimensional striking. If what you want is to just be in great shape and be fit I'd pick Boxing...in MMA even practicing can get you hurt with all these Submissions you're put in and all the Sweeps and Greco Roman throws you get on you.
Mixed Martial Arts is a much more difficult sport than boxing. Why? Because in mixed martial arts you have to worry about getting taken down, getting submitted, getting kicked in the face, getting knee'd in the face elbowed in the face. Mixed Martial Arts is a sport where you have to learn more than just 1 martial art, or you will have a hard time succeeding. Plus, in MMA you have five minute rounds, as opposed to 3 minute rounds in boxing. You will need better cardio for MMA, even though MMA can only have 5 rounds at most, and boxing can have 12, you get a minute of rest between each round. In boxing you get more frequent rest time, so you require less cardio. I do admit that you HAVE TO HAVE good head movement in boxing, or you will get knocked out. In boxing, you only gotta be able to defend PUNCHES to the face or body.. Nothing else.
Boxing all the way
i hope that, it's better for you 'MMA"
I live in Thetford and I'm 13. I'm looking to join a boxing club to keep fit and for fun, but I don't know whether to do boxing or join an MMA gym. Anyone know any local gyms I could join? Thanks.