As far as I know they are not Garmin maps, but still Delorme maps and not really upgradable. Equivalent Garmin GPS unit (gspmap, etc.) have superior topo maps and better gps functionality
They are decent. I would not rely on them for areas that I'm not familiar with. They do seem a bit dated. If you're looking for a true handheld GPS unit that can have downloaded and or chip maps, then i would recommend the GPSMap 66i. It also has inReach built in.