I prefer Jiu Jitsu, I have had more success with it than any other art. I have black belts in Karate and Tae Kwon do as well. I personally believe the best form of stand up martial art is got to be Muay Thai. I have not had the oppurtunity to study it like I wish, however their strict training regimen and fluid movements are bar none the best I have seen in a stand up art. One art the promotes Variety is definitely Jeet Kun Do. It is better to have a series of motions rather than stick to one set form. Honestly Karate will win a street fight about as much as straight boxing. Unless of course you have engaged in some form a street fighting that has rules. Never found that myself but hey you never know.
It is fun and pretty efective, based on natural movement so you dont have to memorize any special techique, you can fight from any position with anything you have available at the time, leg, shoulder, arm, head etc.