They're both good, but for getting streaks the Intervention is the only one you can Qs w/ and get points combos. It's really all up to opinion and situation...
Depends on what I'm doing. Barrett is good for stealth, Intervention for being loud. Barrret will get a silencer and FMJ, Cold Blooded, and Steady Aim or Ninja. Intervention will get Scavener or OMA with Stopping Power and Steady Aim or Ninja. I always have at least one setup with ninja if I need to switch to it if there's a few people using HBS.
I really like the Barrett silenced though. Great for headshots imo.