Native data on your mobile device?

How important is it to have your notes data on your phone/tablet? We all know about working offline with Notes databases but does having native data on your device vs. a web app really make a difference? There are some areas where it is hard to get a good signal, parts of New York City for example. All those big buildings are great at blocking access to cells. If you have a mobile strategy, and I know a lot of you do, would it be valuable to take data offline on your phone/tablet?