Quick reply...
I haven't thought that I would say this:
Ovi Maps are in some aspects better than Modrana

They can do offline routing (Modrana still cannot), they pronounce it turn-by-turn (Modrana can do it, but requires Internet for routing), they use vector data (though Satellite is obviously not vector), they can show 3D buildings (good for showing off Eiffel Tower; not practical), they have ability to show tilted map (Modrana is going to).

So, Modrana will soon catch up.
Ovi cannot log your tracks (can it?), Ovi uses proprietary vector data, while Modrana can use OpenStreetMap.

Fundamental difference: Ovi uses HTML, while Modrana uses Python, and I would prefer XUL.

Some cold water: you need prior written permission of Nokia gate5 GmbH to disclose, copy or duplicate unpublished proprietary information inside index.html