Here's a few posts I have made about KM. Basically, there's nothing wrong with it as an art, but the problem is that there are a lot of scam artists posing as experts.
http://www.sosuave.net/forum/thread...and-got-prices-last-week.223817/#post-2225790
http://www.sosuave.net/forum/threads/krav-maga-effective-for-self-defence.217632/#post-2164629
http://www.sosuave.net/forum/threads/has-anyone-done-krav-maga-training.201815/#post-2000633
Brazilian Jiu-Jitsu isn't supposed to be a street-fighting art, but it will save your life when you are
losing a fight. That's not nearly as fun of a scenario to train, but it is just as important. BJJ will also help you with fitness, and especially flexibility. Mastering a move as simple as a breakfall will save you an expensive surgery or two in the future. Falling down is actually an art in itself; it's a large part of Judo, from which BJJ was later derived.
The consensus advice for mma fighters is to learn a grappling art and a striking art, and I think that advice is good for anyone. Everyone says they don't want to grapple, and that's fine until you get tackled and sat on. At that point, either you know how to get away, or you die. Plus, takedown defense is part of grappling, to learn how to stay on your feet when you choose.
Any one martial art is going to have weaknesses, which is what 20 years of the UFC have taught us. The very first UFC matches are great to watch if you ever get the chance. Everyone brought a 100% pure style. And most of them got their asses kicked, although to be fair, I can tell you from experience that things are very different inside an mma cage. It's like the padded room at the asylum that they lock crazy people in. It was very frustrating to me to be able to throw and slam a guy around, only to have him bounce back up unhurt. A move that would kill a guy on concrete doesn't even hurt, so that is something to think about when you watch the UFC. Yes, those guys are the world's best fighters in any venue, but the way they fight is highly tailored to being inside a very padded cage with a lot of rules.
The other thing that 20 years of UFC has taught us is the list of moves that work so well, they are against the rules:
https://en.wikipedia.org/wiki/Mixed_martial_arts_rules#Fouls Read that list in the opposite, and it is like a manual for street fighting.
If I were you, I would train BJJ, mostly for fun, fitness, flexibility, and low injury risk. Most importantly, it's not going to give you some delusion that you can become Chuck Norris and kung-fu chop five guys at once. That's what the scam artist sensais are selling, which is one of the worst parts of the martial arts business. Deluding someone into thinking they can fight is dangerous to their own safety.