>>4572145I guess I'll answer OP's post since everyone else is freaking out over which is the most effective.
I would argue that karate will give you a sense of community that going to the gym alone or with people you already know just can't. You're also learning something new (unless you've been doing karate forever). Learning new things and facing new challenges are really good for your mental well-being.
I just started BJJ last year and it's great. I have tons of new friends and I get to spar full contact 4 days a week. I'm in the best shape of my life and i am WAY happier than I was before.