The differences between Japanese Karate & Jujitsu are subtle. In fact, both arts include blocking, striking, kicking, joint locks/destruction, and throws. The difference is in how they are utilized and in some cases how they are executed.
In Jujitsu, we use a lot of soft strikes while moving to cause pain and distract our opponent while moving to positions of more control like joint lock/joint destruction, or throws. Karate on the other hand uses joint pain to set up hard strikes from a solid position.
Both jujutsu and karate have throws, in jujutsu you break your opponents balance, often with pain or strikes, and throw him with minimum effort. In karate, the throws are more strength oriented.
In general both arts in our school follow the same philosophy of self defense and escalation of violence. I do only what I need to do. I block first and throw only as a last resort. In jujutsu the sequence is normally: block, strike, take the joint, throw. In karate is is more like: block, strike, strike, take the joint, strike, strike, throw, as in our Ippons.
Brazilian Jujitsu and traditional Jujitsu are COMPLETELY different. Brazilian Jujitsu has lots of groundwork and submission techniques as well as strikes and is often seen in UFC competitions as a dominating style.
Traditional Jujitsu was developed on mainland Japan hundreds of years ago and was used as a self defense by the samurai. Unlike Brazilian jujitsu and karate, it uses weapons such as naginata, katana, and the hanbo. In addition to weapons training, traditional Jujitsu has ground work, falling, throwing, joint locks, submissions, as well as striking. This means that Traditional Japanese Jujitsu, is a complete martial arts system.
As for karate, it developed isolated from mainland jujitsu on the tiny southern island of Okinawa. Its roots go back hundreds of years to Chinese kung-fu as well as to an ancient indigenous marital arts style of Okinawa. A GOOD modern karate dojo (and stress put on good here) will offer an education in self defense using striking, blocking and to a lesser degree, throwing and submission techniques. The one biggest difference between traditional jujitsu and karate is that karate is the art of the "empty hand" or fighting without weapons. Karate fighters learn from training how to defend against weapons, they just don't bring them to the fight. This is because for a long time, weapons were forbidden in Okinawa and those living there came up with karate to defend themselves.
The reason many novices mistakenly believe that karate fighters are bad at ground work is because it is simply not applicable in real-life multiple attacker situations to go to the ground. Although long, drawn out ground work may be an effective way to fight a single opponent, by staying upright the karate fighter is able to take on multiple opponents more easily.