I'm no expert however I have been involved in a few different fighting styles. From boxing, to MMA, and muy thai. Im not a professsional fighter... However have sparred with those who have gone on to figh professionaly. One things I've noticed in any form of martial arts/self defense is the instructors. As many have mentioned... Some can be great and are real students of the art... some strictly preach "THEIR" way, and it winds up being incorrect or ineffective in some ways. One thing I can say for sure is to reasearch the instructor... Try a few classes here and there. However, seeki other instructors as well. Sometimes you can become more well rounded why pulling different skills from different instructors.
My expereience with Krav Maga is limited. However it is much more realistic (In my opinion) than most other martial arts. Taguth to defend against weapons, but most of all end a confrontation quickly and efficiantly. (NOT STAND UP PUSHING AND THROWING PUNCHES TILL YOUR EXHAUSTED)
Just my bit good luck