It takes the same amount of shots to the chest with stopping power as it does without stopping power, so unless they have juggernaut it is pointless
Juggernaut... amazing option, no point in having stopping power, so you might aswell have that little bit more health to protect you from most sniper shots and give you an extra second to turn around and possibly kill them
Double Tap if you have the barrel and Bandolier perk.
Stopping Power if you're using the Apeture Sight or Supressor.
Juggernaut if your crap at the game.