You want to compare the earnings from two different legal forms for a firm: Corporate and Proprietor. Your pre-tax income is $500,000 in both. However there is a difference in the taxes you pay.
1) Corporate pays corporate tax rate of 30%. After paying corporate taxes the rest is distributed as dividends to owners. They pay personal tax on these dividends at the rate 18%.
2) Proprietor pays personal tax on 36% only.