So would you take regular season Selanne over Forsberg?
Generally speaking for the regular season, yes.
There were stretches in their prime for hundreds of games where Selanne was just plain better - such as '95-96 through '98-99. That's 300 games played where Teemu was superior in PPG and massively better at GPG.
Durability is also a huge discriminator between the two. I think on HF durability is really a huge minus because those players don't benefit from the JFK "what if" syndrome. Whereas for the imaginary Forsberg of lore, the sky is the limit. He becomes the most "complete" player ever despite only being healthy enough to play 700 games.
That said I think Forsberg's MVP season is better than any single season Selanne has had.