Try your GPS unit and then try your phone. Enter (or speak) find grocery stores near me. The phone will be right and the GPS will likely only have a few entries. Some of these will likely be wrong due to the length of time it takes to get updated information into these units. I could go on with a variety of comparisons but it really depends upon how you plan to use your GPS.
I drive my RV on highways to a destination so I really only need upcoming turns and lane and traffic information so the phone with Google Maps works perfectly for me in the RV and works 1000% better in my car than any GPS I have ever used.