I guess the biggest advantage of being single is having the freedom. You can enjoy your spare time by doing the things that you want rather than compromising it with the other half's schedule or interests.
On the other hand, the biggest disadvantage would be loneliness. The strong feeling of emptiness may make you want to be in a relationship. As a matter of fact, the human nature is to give love and be loved. Who doesn't like a nice and warm companionship?!