TurboTax' decision which form to file depends on your specific circumstances each tax year.
The 1040-EZ is limited in which tax situations it can handle. The 1040A can handle a bit more. And if there's something the 1040A doesn't include, then you'll file a 1040. It's the IRS who decides which details can go on which forms, and it's TurboTax' job to apply the IRS rules.
One year you might file a particular form, and then the next year a different one.
