Rovaniemi and Saariselkä are both excellent Finnish Lapland aurora destinations. Saariselkä sits further north; Rovaniemi is bigger, easier to reach and has more to do. Here's how they compare.
Aurora
Both are under the auroral oval with strong aurora and clear continental skies. Saariselkä is slightly further north, but on any clear night your odds are excellent in either — chasing clear skies matters more than the exact spot.
Access
Rovaniemi wins: its own airport with direct year-round flights from Helsinki, plus the overnight train. Saariselkä is reached via Ivalo Airport with fewer connections.
Things to do
Rovaniemi has Santa Claus Village, Ranua's polar bears, the Arktikum and a lively city. Saariselkä is smaller and more remote — great for wilderness and quiet.
Which to choose
For easy access, Santa and variety, choose Rovaniemi. For remote wilderness and slightly darker surroundings, Saariselkä. Most first-timers pick Rovaniemi.