Teach gave you a really good run down, but let me add a couple of issues to the mix.
If your state has state income tax, then your states tax treatment of an s-corp is something to consider. At least one state I know of taxes an s-corp earnings, before it is passed through to the owning shareholders. Where it is then taxed on their personal state return.
Since working shareholders (owners) must be on payroll, that is an added monthly expense, so be sure to factor that in too.
The liability protection of an s-corp vs an LLC is basically the same, so though some states allow for an s-corp to also register as an LLC, legally it is useless and is just another cost.
An s-corp has the same record keeping requirements as a c-corp, depending on state laws which specify how often, there has to be at least a once a year documented shareholders meeting where major expenses/purchases, distributions, and dividends are approved by shareholder vote (easy vote if you are the only one, but necessary none the less). The written record gets really important in the event of a law suit, and the courts opinion as to whether or not there is a separation of financial control.