BJJ and traditional Japanese Ju Jitsu are both good. Japanese tends to focus on locks from a standing position, which can be more effective.
Like many grappling arts, they look more beautiful in context to MMA, which is largely sport oriented, but not as realistic in a real life setting.
The truth is you dont really wanna go to the ground, you may wanna learn some in the event you do wind up going that way, but it wont be like what you see in a UFC match or anything like that.
Judo to me can be just as effective.
Japanese Jiu-jitsu: Secret Techniques of Self-Defense: Darrell Max Craig: 9784805313244: Amazon.com: Books
I got this book and it has some interesting stuff in it.