I honestly believe ANY martial art is beneficial, as long as the instructors are decent and have a good attitude (ie. avoid the "clubs" that promote fighting rather than self-defence).
I work for the government in a capacity which brings me into contact with aggressive and often dangerous people on a daily basis. I also teach Tae Kwon-Do (traditional style, not the "sporting" version you'd all have seen at the Olympics and so-forth). In saying that, in seven years I have never used a specific Tae Kwon-Do technique to defend myself at work. BUT, the training itself has enabled me to avoid being hit and injured, as well as provided me with better reactions so as to enable me to better deal with violent people.
In the past I have trained in shaolin (wu-shu), zen do kai, karate, judo, and various weapon styles. They all have something to offer. Their suitability for any particular person usually depends upon that individual. If you want some basic defence training (and nothing more), karate or a similar linear style is probably most appropriate. Jui-jutsu is great for grappling, and tends to suit those with a more "robust" body. Aikido is awesome, but is almost impossible to use as an offensive tool (you have to be attacked to use it effectively). Tae Kwon-Do is great if you're wiry and light on your feet (but yes, it is primarily a "keep them at a distance" style), and although it places a lot of emphasis on kicks it still utilizes effective hand techniques and, believe it or not, grappling. And in saying that I must add this - there is nothing wrong with jumping. If you do something often enough, you can use it effectively. I have proven this myself time and time again against people who tell me that jumping and head-high kicks are useless. But I digress ... I'm not trying to say Tae Kwon-Do is the best style .....
What I'm saying is THERE IS NO BEST STYLE. Try several different arts and see what suits you. If you want to immerse youself in a martial art, kung-fu, aikido, etc is the direction to look. If you want some basic training (in other words: if you don't want a black-belt etc), look towards an art with a simpler system. What I mean by this is: if you do karate for a few weeks you will probably be better able to defend yourself. If you do kung-fu for a few weeks, you really won't achieve much because it is a much more complex style to understand. In saying that, I'm not putting either style down - if you matched up two similar people who had been training in these styles all their lives (one in each), I don't think you could easily guess who would win. They just have different learning curves. And don't overlook things like boxing - the best kick-boxers are usually ex-boxers (and there's a reason for that - boxers learn how to hit, and take a hit, really well).
If any of you disagree with me, feel free to argue. But truthfully, it won't get you anywhere - most concepts have to be demonstrated rather than explained. But I'll humour you, if you humour me, and maybe we can both learn something from it.
