The quality of any martial arts training will depend much more on the teacher than the art being taught. A bad teacher can ruin any art, but a good one will teach you important things about yourself (your limits, your strengths and weaknesses, and how to change them) under the pretext of any art.

Personally, I've been training Isshinryu for ~9 years. It's been great for me, in terms of keeping me in shape, relieving stress, and learning confidence and discipline. Isshinryu is a striking art, but we also practice judo and grappling to a lesser degree. I actually wish we did more of those two, because many fights end up on the ground, and I feel underprepared for that -- though many of the people I've trained with have learned judo or wrestling separately, so it's possible I'm better prepared than I realize. (The evidence is still there, though. I rarely won on the mats. =P)

As far as starting a martial art, just find a dojo and go. Most will welcome you to watch a class so you can get a feel for the style and the instructors. Your first few weeks practicing can be embarrassing for some. Don't quit. Nobody there is expecting you to know what your doing, and you'll adapt to the dojo's norms pretty quickly.

The main thing, though, is to find a teacher who knows what they're doing. Also important: make sure you respect them. As long as you have these, your martial arts training will definitely improve you. No guarantees about making you into an unbeatable street fighter, but you won't be disappointed.