Good luck trying to find a legit JJJ club in anywhere but japan. JJJ is more about standup than ground, its also more self defence orientated (not that BJJ isn't) its a pretty faded art I believe, I don't know anyone that does it, and if they do its probably taught at some mcdojo. BJJ is more effective and about groundgame than standing, and these days its big for competition.
I have never been a practitioner of either to be able to get into great detail. But my former kickboxing coach used to teach me some JJJ. I learned some of the same types of locks & holds (arm bar, rear naked choke etc..) but mostly focused from a standing position, so it included numerous takedowns - some that are similar to judo, and some that are undoubtedly used in modern day law enforcement, then once on the ground there were familiar submissions. So all in all, my experience is pretty consistent with Bumpy Knuckles' comment.
In BJJ your not allowed to twist a guys balls for submission. Thats why you should never try to twist a Japanese persons balls in a street fight if you suspect he knows JJJ, those *******s are so practiced they will jjust smile at you and actually let you twist their balls to set you up for a counter while your overly focused on how the guy cant be screaming by how hard your twisting his balls. Plus dont ever let one of those guys get ahold of your balls or just say good nite.