After looking at samples of both Finnish and Swedish, I have decided that if I was a Troll, I would definitely speak Swedish. First, it sounds more gutteral and orcish, so I could growl more effectively in it. Second, the Swedes conquered Finnland for a short time, which is in keeping with Troll lifestyle. In fact, I think they were motivated to overrun Finland because Finnish has too many words over 9 syllables.

That said, a lot of joiking is done in a language called Sami, which is neither Finnish nor Swedish. It belongs to the Sami people, who preceded the Finns and Swedes in that area. They span several national boundaries. Purportedly they live in inacessible areas where they joik, herd reindeer, and speak a secret language.