LLC and S-Corp's offer the same level of protection, the same system and forms for taxation, and function similarly. In my state, for the S-Corp we must file a simple form every two years for the S-Corp that does not get filed for the LLC. This form just lists the names and addresses of officers/board members. In other words, in practical terms, there is little difference.
My construction company is a Sub-S (since 1982) and my property management firm is an LLC (since 1998).
There is a little more paperwork in establishing a Sub-S. You must first establish a Corporation then apply for Sub-S status with the IRS. It's just a little more paper.
You should do one of them prior to the first job. Do everything in the name of the entity, not your own. Starting out makes everything easier and cleaner. Switching later will require new licensing, insurance, phone, supplier accounts, etc.