While I would really rather that they both start somewhere... I think Paxton would be the choice for the pen for a couple reasons.
1. Paxton probably has the lower innings cap for this year (my guess of 180 innings tops) versus Karns of probably 200 innings
2. Paxton may benefit from throwing less innings early to build up the strength in the finger / fingernail as well as other body parts... even with the loss of weight.
3. While Dipoto only wants 2 lefties in the pen, I still wonder IF Furbush will be at full strength to start the year... and how many innings Charlie will be allowed to throw based on last year's injury.
4. I really really want to start to hear all the hype start early on what a STUD Paxton is from the national media as soon as possible... and that won't happen in Tacoma.