Different results from different tax prep programs?

Factual Questions
1

I just wrapped up my taxes, and had the luxury of being able to use three different programs. Glad I did…

The players: H&R Block’s TaxCut, both the web-based version and the installed application on my PC, and TurboTax Online.

There was a nearly $140 difference in my Federal taxes from these three. Each managed to arrive at exactly the same amount for my state return. Why is there such a large difference for a single person with one W2, one 1099-INT and two 1098s for the mortgages? As tax returns go, this isn’t much more elaborate than a 1040-EZ filing.

What really surprised me was that there was a difference between the two H&R Block products, since they’re probably using the same core “engine” - not that there should be any difference between an electronic filing and one done on a paper 1040 and Schedule A. If I had the forms, I’d be tempted to do a paper return for comparison.

Any tax mavens care to explain this?

2

I would look at how the programs filled out Schedule A. They must have had differences in the amount of itemized deductions.