I have done both and loved (and hated) both.

Self Employed Pros

1. Freedom!  You work as much as you like, when you like, where you like and dressed in what you like.

2. Money!  A successful freelancer or consultant can make significantly more than the same job as an employee.  And there are tax benefits.
I earned 40% more in one freelance gig when compared to the same work as a fulltime job.

3. Sanity!  A consultant does not need to attend 8-hour department meetings, travel at peak commuting times, or get embroiled in a politics.

BUT!!!

Employed Pros

1. Security.  You are less likely to be let go off because you are an employee.  Cuts often happen with the freelancer.  You also are being developed and are not usually judged on a single project like a consultant.

2. Future!  As an employee in a good company you have a career plan, you have opportunities for advancement and you are around for the long term.

3. Control.  As a freelancer you have to please your boss or your client.  You don't usually make strategic decisions and you rely on other people to give you direction.  As an employee you can become the boss and control your future.