We have used VZ Navigator (pictured) for a few years and have found it to be reliable.
One of the few complaints from users is the inability for VZ Navigator to interact with Google Maps. In fact, it won't allow the use of any third-party software.
We considered switching to Sprint several months ago for sentimental reasons because I was an auditor for Centel and Sprint purchased Centel in the early 1990's.
Sprint Navigation failed a live comparison test. We entered the same address using voice commands.
Both VZ Navigator and Sprint Navigation got us to our destination. However, Sprint Navigation took us off arterial streets and onto side streets for part of the route. VZ Navigator kept us on main streets.