You can search for places (and actually find them) offline, get transit directions and navigation, all without an active connection. Google Maps - as good as it is online - does not support those two features.
Now, as good as all of that sounds, we should note that offline usage might not exactly be the mass use case. Also, Nokia Maps is only available on Windows Phone, and given Android and iOS’s popularity, that’s one huge hurdle. Still, if you want one compelling reason for using a Windows Phone device, Nokia gives one in this video.