S corp, tax rate based on indivual tax rate up to 37%, S corp has QBI 20% deduction, which can reduce its tax rate lower. But you have to distribute all your retained earnings as distribution through K1. 

C corp, tax rate is 21% flat rate, C Corp is not eligible for QBI. However, you can keep the profit as retained earning with the business. You are not necessary to pay double tax if the profis does not distribute to you through K-1. 

Also, If you own a C corp over 5 years, no capital gain tax if it is sold. But if you sell a S corp, you have to pay capital gain. 

Based on these factors, which one is a better choice for tax saving for a business owner?

Are there any other factors to be included for this comparsion?