Most people misunderstands the real sence of martial arts. Yes, you are right if you think that they all are more or less the same in some broad aspects: they all demand an important dedication of time and muscle-&-mind’s power; and for the ordinary woman or man that does not know much about martial arts, Jiu Jitsu and Tai Chi or Wing Chun are as much as self defence techniques, which is not just like that... Tai Chi is not precisely a combat’s art which would teach someone to destroy enemies in a snap, nor is Jiu Jitsu or Judo (although, well, you better don’t dare to disturb a black belt judo – ka!!), but a Muay Thai fighter you would rather have as a friend... He or a Tae Kwon do fighter, well, you better keep them as friends!
Martial arts are much more than self defence techniques; in almost all cases, the interested that follows the path of one or more martial arts learns early that the best defence is to avoid violence; even if you got the power to disable your opponent(s) in less than snap. So, a real martial artist is not a killer machine, but a peaceful human being that has identified a way of living his or her life in armony with the body, the mind and the society.
Of course, there are some other martial arts that exclude that pacific mysticism far away from the art, and, for instance, mister Bruce Lee’s Jeet Kune do is a compendium of attack techniques mister Lee had studied during long time and which use against an adversary may cause him severe damage...