The difference, a very big one, is that in 2020 (and now 2021 also) cash deductions to 50% charities are 100% deductible, without subject to limitation. You can also use prior-year carry-forwards and carry forward any excess. So it's now possible to pay zero tax regardless of income if you itemize and have significant contributions. The program in Step-by-Step doesn't treat this properly, though the Forms version appears to be correct.
