I've been Nokia user since a long time and so I've always had Nokia maps pre installed in my device.
But still I always prefer Google maps over Nokia maps. There are various reasons. Firstly let me say why you should have maps on your phone.
Earlier this year, I had gone to another city for attending a conference. The distance between guest house where I was residing and the conference hall, was quite long.
Being new, I didn't know any route there. Ofcourse I could have asked people near by, but in past, I've had couple of bad experiences asking for directions so I no more ask for directions. That time, Google maps helped me alot.
I'd say everybody should have maps on their phone, be it Google maps or Nokia maps or other. The reason I prefer Google maps is because:
1. Simple UI:
All those who've used Google maps, know that how quick the loading takes place in Google maps. I believe it is because of UI that it uses. I've compared loading time between Nokia maps and Google maps by searching for a place, using same internet connections. The search results came pretty much at same time but when I clicked on the place, Nokia map took almost twice as much time as Google maps took. The time decreased when I switched over to 3G network but if I'm getting better time in 2G network using Google maps, then I don't see any reason that why I should continue using Nokia maps.
2. Saving favourite places and availability across every platform:
Adding star to favourite place is a common feature that is present in every map these days but availability is a major factor. For example if you're using Nokia then all the favourite places are synced using your Nokia account. But what'll you do if you migrate to other brand or platform, say Android? This is biggest advantage of Google maps. It is available for every platform, be it Android, iphone, Symbian, etc. For syncing, you'll need a gmail account. So when you migrate from symbian to android, all you need to do is, download Google maps and sign into it. Syncing will take place and all your favourite places will be shown again.
3. Latitude feature:
Ever wanted to know where your friends are? Google map's latitude feature allows you to do so. After you log into Google maps using your gmail account, click on Join Latitude. Then just add your friends who are using Google maps. You'll need to wait till they accept you for sharing their latitude with you. Once they do, you'll always be able to see them on your maps. You can opt to sign out from Google maps anytime to stop sharing your location. And remember to click Yes on exit when Google maps asks you that whether or not you want to share your locations.
To download Google maps on your device, visit m.google.com and select maps via your inbuilt browse.