Does TurboTax software compare married filing jointly vs married filing separately to suggest which is better for you?

No.  if you want to do this, you may be better off with the desktop software, if you have a compatible computer, because you can prepare all 3 returns for 1 price and decide which to use.  if you use online only one return per a/c so the second return would wipe out the first and the third would wipe out the second.  you may also need to pay first to review the returns.

generally joint is best.  certain credits and deductions are lost when married filing separately.

one rule that must be followed is if one itemizes both must itemize and if one uses the standard deduction both must use the standard deduction.