Use my Garmin705 for biking and for navigation on both bike and car while traveling. It has worked out real well for both. However, on two occasions, one in FL and one in CO, the thing took us on a complete circle of roads before steering us on the correct path. First time it was irritating as the circle was a couple miles in strange territory. Second time it was sort of funny because it took us out one driveway, down the street to another driveway, back into the parking lot, then out the first driveway and turned us the correct direction. Total of less than a block.

Only disadvantage is that the screen is a bit small for night driving solo.

I don't like using the smartphone for communication and navigation. From what others have told me too often when they need the smartphone for an urgent matter the battery is done for by all the navigation. Don't put all your eggs in one basket.