1 week Lapland trip in December: need help choosing itinerary

Planning a Lapland trip Dec 10–17 with my father. Flying in/out of Rovaniemi. We love snow, winter scenery, northern lights, nature, skiing. First time in Lapland.

Trying to decide between these itineraries:

1. 4 nights Rovaniemi + 3 nights Levi
2. 3 nights Rovaniemi + 2 nights Saariselkä + 2 nights Levi
3. 3 nights Rovaniemi + 1 night Saariselkä + 3 nights Levi
4. Something else?

Would you prioritize Levi or Saariselkä for a first Lapland trip in mid-December, or is it worth combining both?

I’d really appreciate any advice. Thanks!