Do what ever interests you but don't overlook the more competitive arts as a good starting point for building a base skillset. If you're interested in striking Muay thai or boxing will ensure you know how to be a formidable striker and will teach you to deal with aggressive strikers. If self defense ability and fighting prowess are what you're after train in a system that regularly spars. The best way to get good at fighting is to actually fight, preferably in a controlled setting with qualified professionaks who actually have been in fights themselves (and not just a street scuffle or two).
Ninjutsu and krav can be decent add ins once you already have the ability to control an aggressive attacker. But a lot of these schools don't emphasize sparring and won't teach you the nuances of timing, controlling distance with an aggressive partner. For self defense it's good to have some knowledge of more aggressive and combative options but you can't throat punch and knee stomp every person that gets physical or threatens you. If you have a solid base you can dodge and avoid punches and maybe even the fight all together, but you don't want to rely on highly aggressive techniques for every scenario.
A lot of ninjutsu, traditional jujutsu, and aikido uses compliant training as the main form of technique transmission. It may have its value but it's very far from reality. If a class spends most of its time on compliant technique I'd seriously consider what you're after.
Ninjutsu and krav can be decent add ins once you already have the ability to control an aggressive attacker. But a lot of these schools don't emphasize sparring and won't teach you the nuances of timing, controlling distance with an aggressive partner. For self defense it's good to have some knowledge of more aggressive and combative options but you can't throat punch and knee stomp every person that gets physical or threatens you. If you have a solid base you can dodge and avoid punches and maybe even the fight all together, but you don't want to rely on highly aggressive techniques for every scenario.
A lot of ninjutsu, traditional jujutsu, and aikido uses compliant training as the main form of technique transmission. It may have its value but it's very far from reality. If a class spends most of its time on compliant technique I'd seriously consider what you're after.