It's funny to hear smart phone vs. GPS debates. It is like the fast & light vs. the heavier & prepared debate. There are pros and cons to both.

The fast & light crowd would only take the smart phone. The more prepared ones making sure all of the right maps are available ahead of time. The unprepared ones hoping they will have data access, let alone phone coverage, wherever they are going. All of whom burn their battery to support their navigation and hope they will have enough left for possible emergency communications. The prepared may carry charging devices, solar panels, or even a PLB. But now you're carrying enough stuff to carry a proper GPS to begin with. Advantages of a smart phone GPS do include a color display, updated maps, potential data access, and less equipment to carry. But if we updated our GPS units like our smart phones, they would be just as colorful and updated. They'd also be waterproof, nearly drop proof, easy to read under any light condition, have all the TOPO and city details already loaded on them so they're always ready to go.

My rule of thumb, if you are going somewhere where you plan on relying on a GPS, take a real GPS with you! A smart phone is convenient for times you don't plan on using one, but anytime you plan on using one, take a real one. Finally, when it gets down to it, as an embedded software engineer, I NEVER depend on electronics. Always have a compass, environmental based navigational skills and at least a basic map with you when you head for the backcountry.