Read the answers to this question: [What's the difference between primary & secondary fermentation?][1]

I am an advocate of **not** racking to secondary. To answer your question:

## Advantages ##
(of not racking)

 - Reduced risk of infection
 - Don't need as many vessels
 - More time for trub to settle (racking can disturb the trub if you have to move your fermenter)

## Disadvantages ##

 - Risk of [autolysis][2] (low IMO)
 - You don't get to "play" with your beer

## Bonus ##

I do not rack to secondary and still get very clear beer.  After kegging I cool the beer to the low 30's F for a week or so to brighten. Crash cooling drops a lot of protein out of suspension.  The first pull is pretty goopy, but the rest of the keg is pretty clear.

Pro brewers do this in a separate tank called a brite tank.

If you bottle you can get the same effect by racking to your bottling bucket, sealing that up and crash cooling it for a week in the bucket.  Be *very* careful moving it, or bottle straight out of the fridge.


  [1]: http://brewadvice.com/questions/87/whats-the-difference-between-primary-secondary-fermentation
  [2]: http://www.homebrewtalk.com/wiki/index.php/Autolysis