I perfer the Google Maps approach for several reasons. First, my #1 priority for a GPS system is it's POI database. I would actually prefer an always online approach since you constantly get the most up-to-date results. All of the other features are more or less a wash for me after that.

I will commend Nokia for the improvements in Ovi Maps, but for me and my use cases it is nowhere near the features and usability of Google Maps.

I have loved my n900, but its one area that desperately needs improvement is in its mapping application.