I don't get why more people aren't saying they use Garmin, it's the gold class gps mapping choice.
Garmin gets their map data from NavTeq which is now part of Nokia (HERE maps devision). And while the data used to be the "gold" standard, it certainly isn't today.
Have you tried submitting error reports to Here/Navteq lately? I have, it takes anywhere from 6 months to 2 years before the fix shows up in a map update. Go to GPSpassion forums and see the countless of errors reported in 2012 that are just now making their way to the City Navigator 2015 packages.
It also depends on your location but for most users on dedicated mapping/GPS forums, in terms of map updates and data accuracy this is the order I've seen:
1. Google Maps
2. TomTom (data for Apple Maps) - distant 2nd but getting better
3. Navteq/HERE (data for Garmin)
As much as I hate to admit it, it's near impossible for anyone now to catch Google in this space.