While I have smart phone map apps, I really don't use them but rather my Garmin GPS. Reasons:
1. I don't have to physically hold in my hand the Garmin while I am driving.
2. The Maps on a Garmin screen are larger and thus easier to read while traveling down the road. Easier to read the map at night when driving. The flexibility of being able change my route and then have Garmin reschedule the route.
3. I like the audio prompts telling me the road names, traffic conditions, school zones and step by step directions to my destinations.
4. I like the visual warnings when I am going over the posted speed limit, the estimated time of arrival.