Starting on our knees, and with no faul techniques allowed, I have been beat by most BJJ guys I have rolled with.That is their game, grappling on the ground.
Starting on our feet, different story all togehter. Their throws (lacking) and takedowns ( decent) were enough to make them good matches, but I did ge the better of them most of the time.
Working against guns, knives and clubs ( training ones, we aint that weird) the BJJ guys I have trained with are really lacking, one is now our student, as he realized he spent the last 2 years learning how to win grappling tournaments, but our stuff fit him better as a Federal LEO.
Now it does depend on the Dojo and Sensei though, I know ther are BJJ instructors who teach with self defense in a more promanint role, like my freind Steve Maxwell, just as ther are JJJ Dojos that are teaching fantasy fighting.
This is not a slam on BJJ, just my experiences with it and my outlook on JJJ as a 2nd Dan in it. I personally crosstrain with BJJ guys as much as I can, Grappling can happen, sometimes you want to take a guy to the ground and control him, especially if your not out to maim or kill him, grappling is great for the drunk buddy, who decided to try you.
It also can be forced on you, and not being able to handle yourself down there can be very bad indeed.
As another pointed out, your attacker on the street probably wont be another dedicated martial artist, but he might be a very successful street fighter, and armed, that's why I choose for my primary art, one that teaches Throws, Neck Breaks and chokes, joint destructions and controols, takedowns, sweeps, moving people into objects and walls, very hard, defenses against guns,knives, clubs, garrotes and other weapons, along with many of the same grappling techniques found in BJJ and a few that are not.
I do like BJJ though, I just feel it's a component art, like Boxing, whereas Jujutsu is a complete art, very comprehensive.
Nothing is the best, just best for the individual, and I love Jujutsu,but I also study Pekiti Tarsia, Silat and I shoot a bit.