It gets tricky when your profits get high and the effort of setting up and maintaining an S-Corp becomes more questionable. The 12.4% Social Security stops at $132,900 (2019) in income so if you want to max out a solo 401K (assuming a 25% employer contribution) you'll need to have $148,000 in W2 income ($19K from the employee and $37K from the employer to hit the 2019 limit of $56,000).
So at that point you've already paid all of the Social Security tax possible for the year and the S-Corp advantage is greatly minimized as you only continue to save on the 2.9% medicare tax. That's still something though as there is no cap on that tax.
S-Corp is significantly more work than a standard LLC. You'll have a separate corporate tax return and use the K1 for your personal taxes. You'll have to run payroll as you as an owner will now be a W2 employee and deal with workers comp, unemployment and all sorts of other fees and taxes depending on your state (for example here in WA they just started a paid family medical leave tax on gross wages up to $132,900). Some you'll be exempt from as an owner/employee and others you won't.
There is a lot more to the subject for sure, but those are a couple of highlights to dampen the mood of the idea of huge tax savings...
