@sherwood In my opinion, the main reason for using a corporate structure is not to save on taxes, but to limit liability.
People file lawsuits all the time. If a someone my business and it's a sole proprietorship/partnership, my personal assets are at risk. But if they sue my business and it's a corporation of any type, only the business assets are at risk - they can't touch my house or personal savings.
And if you're going to be a corporation to limit your liability, it only makes sense to be a tax-advantaged one (sub-S or LLC) instead of a C-corp, which results in double taxation (corporate tax + personal income tax on dividends paid out).
Also, using a payroll service is not a requirement. You can handle your own payroll and related tax filings (my business does). Payroll services will pitch their use as having the advantage of limiting your liability - they'll cover any fines for filing errors, which do happen from time to time. But if you're careful, you won't be fined very often or very much... over the course of my career I've paid about $200 or so in payroll associated penalties, but doing payroll myself has saved well over 100x that on what I would have spent on an outside service.