Really have to hand it to the Finnish pilots. I imagine differences pilot skill/experience and tactics had a great deal to do with the kill ratio too.
Absolutely. Finns adopted German 4-finger and pair formations already before the Winter War, while Russians were still sticking in tight 3-plane or even bigger formations, where wingmen were just following the leader. And when he was killed, they didn't know what to do. Russian way, boss gives orders and initiative was punishable. They learned during the war, anyway.
Here is very good description of tactics used and B-239s in Finnish service.