Its not the art its the training method that makes a good fighter. If you are not actually fighting with UFC type rules or less then you are not prepared to fight. They call this training 'alive'. Aikido, WC, TKD etc all train without this aliveness. Judo, BJJ, Boxing, MT kickboxing, etc all train with aliveness. Fights arn't perty, its dirty ulgy stuff. If you are not taking shots to the face on a regular basis then you wont know what to do when you take a shot to the face. You will get the adrenaline dump and flip out. You will panic, flail, and be in a worse position. Take for example karate. Most karate focus is on forms and point sparing. These people will not be able to fight. But there are branches of karate that focus on full contact fighting (kyokushin karate for example). These guys are hard core, they will know how to fight. All they need to do is add some clinch and ground skills to cover all ranges of hand to hand combat. This brings me to the second point of self defense, you have to train to fight in all ranges.
Fights are not just boxing, or wrestling. They are everywhere. To be a good fighter you need to know how to strike, clinch, and grapple. Very few martial arts cover these ranges, and even less train with aliveness. This is why the best fighters are usually MMA (mixed martial arts) fighters. You will see them pick up a striking art (Tipically MT) and a grappling art (judo, bjj, sambo). This lets them be effective in all ranges. Sure their focus is usually in a single range, but they make sure they wont get wasted in the other ranges.
I didnt use to belive this was true. I studied TKD for 6 years. I had a blackbelt and thought I was an all around bad boy. My instructor died in a car wreck and I started looking for a new school. I ended up in a kickboxing school and was put away in no short order. It was the first time in my life I had been hit full contact. I had an adrenaline dump and did not know what to do. I ran from this for years, studying all sorts of crap. krav Maga (not saying its crap, but the school I trained at didn't fight full contact), hopkido, karate, and fianlly aikido over the course of the next 5 years. All of them looked great, but none of them made me feel like I could defend myself (and I was still refusing to belive that I needed full contact fighting to learn how to fight). Finally, with enough lurking on bullshido.net and pushing from my aikido instructor I got into judo. I've been training in judo for a few months (almost 6) and I've also started taking Gracie Jujutsu (BJJ) classes for the last 2 months with the ocasional MT kickboxing and NHB training thrown in (the gracie school trains for vale tudo). I can honestly say that I have learned more about real fighting in 6 months then I have learned in the last 11 years of my life. I'm almost 26 years old and I plan to be fighting NHB/vale tudo fights by the begning of 2007. Possibly sooner if I think i'm ready. After I got over the shock of actually getting hurt and learning to deal with the adreanline rush that comes from taking punches and chokes/armbars. I find I can now slowly start to actually use the stuff I learned over the last 11 years.
My wife says what I'm doing doesn't look as good as aikido did. She says its hard for her to see who is in control and winning, and that a lot of times she thinks i'm beat and I tap the guy out with a submission. I guess real fighitg doesn't look perty. It doesn't look like TKD, or aikido, or Hopkido. Its sweaty and bloody and in the end you only worry about what works, not what looks cool and has the uber kill shot skills. Most of those cool techniques are very low percentage and normally wont work without 10+ years of training.
So I guess my point is that I've learned that if your not really fighting, then your just training a sport with very little real use for self defense. All the aikido training in the world didn't help me in sparing with a guy who knew how to strike. All the TKD training in the world didn't help me sparing a guy who knew how to grapple. What helped me was knowing how to relax, and use the defenses I drilled a thousand times against. I dont worry is this jujutsu, or is this aikido. I just do what looks like it will work the best. Sometimes I get beat, sometimes I win. But slowly I'm removing those low percentage bad techniques I learned, keeping the good ones, and adding new high percentage techniques. Its just so sad how much of my previous training was low percentage techniques that rarely work. Oh and I still train aikido now and then, but no one in the class but the instructor can actually do techniques on me with out me letting them. I guess it just takes 20+ years to have working aikido (of course he's also a Japaneese jujutsu guy...) So I dont do aikido for defense anymore. I train it for timing, balance, flexiblity, and just because its fun to hang out with all my friends.