Iginla has been a pretty slow starter at times in the past, Kessel has been a fast starter since he became a regular. That alone makes me think that Iginla is just off to a slow start like last year and he will get going after about 15 games.
It wouldn't surprise me if Kessel does better, I am just going with my theory and saying Iginla.
Kessel, and I have a feeling both will score under a 30 goal pace (over a full season) which is rare for them. Iginla is declining though I do expect him to pick it up soon, and Kessel's goal scoring has gone down ever since the new coach and also Lupul is out.