Just because the word fruit or vegetable is in a products name doesn't make it as healthy as the real thing. Advertising and marketing do wonders for something that isn't worth buying.
The biggest difference between juices and fruits or vegetables is fiber content. Fiber keeps you full for longer since it takes a while to go through the stomach. It also has been shown to lower cholesterol levels and reduce the risk of colon cancer.
To make juices easier to drink, it is filtered and much of the fruit (the part that contains the fiber) is missing from the juice. A lot of juices are also loaded with extra sugar which adds to the taste but speeds up the digestion process and does not help you stay full for very long.