Advantages:
-Faster growing times (Don't have to wait for a seed to mature, the plant begins matured)
-If one plant is good, you can get crops of quality plants that you like
-It's easy, very easy...After some experience you can probably get about an 80% success rate.
-You don't have to germinate seeds, which is more risky, and seeds are expensive depending on what you growing
Disadvantages:
-You have to keep one or more 'mother' plants which can usually last indefinitely, but requires all the treatment of a normal plant. (To cut branches from)
-Space can be a problem, if you don't have enough