@Richard: Aikido has a shitty reputation because all people see are guys in long skirts running around doing fancy rolls and backflip. Most people who try it dismiss it immediately because "no one would attack you like that in real life". Heh.
The reality is that I first learned Aikido from a bunch of black cops who patroll downtown Richmond, VA. Let that sink in for a moment. These black cops who are used to dealing with shitty neighborhood in Richmond teach Aikido, and believe it's a good idea to incorporate it into their job.
Japan police have to learn aikido in order to gain certain promotion.
When you consider that Aikido was developed by a tiny, psychotic and sadistic Japanese badass (no disrespect to O'Sensei) who fought during the war, interrogate prisoners and train the Jap special forces, then survived the war, you really oughta think twice before dismissing it.
The problem is, after his "enlightenment" he decided to "hide" all of his techniques, so you end up seeing a bunch of choreographed moves with some guys in skirts. Very very few Aikidoka even understand why the techniques was done in a specific way. The fancy looking kotegaeshi and shihonage techniques in reality are just wrist break or arm break accompanied/preceded by a jab to the face. Apparently if you do it that way you run out of training partner pretty quickly, so that's why...
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Back to the matter. If you want to learn self defence it's best to begin with something with a fast learning curve. Aikido is extremely effective and deadly (its main techniques come from Jujutsu, which were used to defeat armored samurai) but you need to be able to apply it. That means good footwork, body coordination, how to hit and how to NOT get hit first.
Aikido is pretty bad as a starting martial arts but is a fuckhuge force multiplier if you incorporate it into something else. Aikido teaches you ample movement and dodging (big deal IRL), the basics of dealing with weapons, and, as far as I know, is the only system that teaches defense against multiple attackers.
Really, I would take aikido just for its emphasis on situational awareness. The best fight is when you are not there.
Plus, it's probably the only martial arts that's gonna make you look good in court. Aikido's submission hold/choke are peace makers and if you can/want to pull it off you avoid a shit ton of headache. Truthfully the majority of violence a modern person might run into can be easily diffused by just walking away, or failling that a submission choke. Throwing a haymaker or breaking his bones will cost quite a lot in lawyer fees even if you are the victim.
This right here is Aikido done right. Never know when you might get attacked by trans feminist
Great thing about Aikido is that it's a journey that changes with you. You can do it at 4 yo, at 18, 30 or 60. Can't say the same for boxing.
If you are dead set on using similar art, learn Jujutsu. Bigger brother of Aikido.