Shotgun or Pistol as a sidearm in MW2?

My primary is a SCAR-H with ACOG. I use Commando, Cold Blooded, and Scavenger. I don’t usually run around the whole map trying to get kills, but I don’t camp either. So I’m kind of in between. Which would be best for me? I was thinking of using the SPAS-12 as the shotgun or the Magnum as the Pistol. If you think I should use another shotgun or pistol besides the ones that I listed, go ahead and say it.