Vector quantization lowers the bit rate of the signal being quantized thus making it more bandwidth efficient than scalar quantization. But this however contributes to it's implementation complexity (computation and storage).
Advantages:
Small file size
Unlimited zoom without anti-aliasing "jaggies"
Good for line drawings and images with large areas of same color
Disadvantages
Can not reproduce photographs well
...
There are a few.
Vector graphics are more "scalable" than raster graphics. By this, I mean you can draw a design that's six inches high, enlarge it to four feet high, and still have it look sharp....