Both sections can be appropriate places to enter it - but you will only enter it once.
Some people have property taxes listed on their Form 1098 along with their mortgage interest (usually when the taxes are paid via escrow). So, TurboTax provides a method of entering these taxes right on the same screen as mortgage interest.
For those that don't have them listed on Form 1098 or maybe don't even have any mortgage interest, TurboTax has a separate entry area for just property taxes so those users don't miss the deduction.
