Thinking of it in these terms helps me keep them seperate.
"Normal" jujutsu = Japanse Jujutsu: "Oh Crap! I dropped my sword, but you still have one." This leads to a set of techniques that focus on bypassing the brunt of an attack (sowrd strike), then seizing and controlling the guy who still has a sword by entangling the joints of his body (usually wrists, elbows, shoulders, & neck) and bending them in un-natural directions. In time, the sword has been replaced by the right cross or beer bottle.
Brazilian Jiu Jutsu: "I know something you don't know". Martial arts took stand-up fighting to an Nth degree of sophistication. The Gracies come along with Old Judo, blended with positional transitions from wrestling, and pull the poor karate guys to the floor where they can't use their really cool moves, then choke them till they turn funny colors. An analogy I loved from the early days of BJJ, used by guys who switched in from other martial arts, "It's like the martial arts is a three-sided fortress with the back wall missing, but nobody ever noticed it wasn't there until the Gracies slipped in from behind and stormed the castle, easily. We just simply forgot about that wall."
If you had to fight a shark, you would probably prefer to stay on land where the shark is at a strategic and mechanical disadvantage. The Brazilian JJ = shark in the water, trying to pull you into the tank to have their way with you.
Japanese JJ = somethine really useful to know. Not a lot of guys with swords out there, but tire irons and ball bats are still an option for the less-than-honorable.
Search the web and read a bunch; there's a lot of stuff out there on both.
D.