denny...An s-corp is not taxed twice as you have described, all profits at the end of a year of an S-Corp are taxed at the owners tax bracket. One advantage of an S-Corp is the ability to take "disbursements" of profit thru the year that are not subject to social security and medicare tax.But these disbursements can't be larger than the pay you take from the corp. or the IRS could reclassify them and come after you for taxes owed plus interest,etc.
A C-Corp's profit is taxed at the end of a year and then again when an owner pays himself, which is a form of double taxation. C-corp is for a larger company with large profits in my opinion.
I don't know much about LLC's, but think they were originally designed for partnerships.Most states now allow one owner LLC's.
As far as corporations totally excuseing you personnaly for liabilty....that depends. My attorney says a corp is just another "bump" in the road to your assets if you are sued. For instance, if you are negligent on an installation that causes property damage or personal injury, its possible for a savvy attorney to sue the corp. and you.
I Inc. myself mostly for protection from employees possible mistakes, and for the disbursement advantage. If I were wiring alone, I would go back to being a sole proprieter and avoid the yearly Inc. fees and the added Inc. paperwork.
I got a book on Amazon called "INC. Yourself" by Judith H. Mcquown that was very helpful in my decision to INC. myself.