Tactical Mask | Tactical Mask Pro
Ability: Protects you against NOVA GAS.
Pro Ability: Tactical Mask Pro reduces the effects of flashbangs and concussion grenades, it also reveals the position of a flashed or stunned enemy.
Marathon | Marathon Pro
Ability: This extends your sprint time, but it doesn't increase your speed.
Pro Ability: Gives you unlimited sprint.
Ninja | Ninja Pro
Ability: Ninja allows you to walk, sprint and jump almost silently, therefore you can sneak behind enemies more easily. This is the equivalent of Dead Silence from Call of Duty 4.
Pro Ability: When you have this equipped enemies will be louder, it also makes you completely silent.
Second Chance | Second Chance Pro
Ability: Gives you the ability to survive a normal death by dropping you to the ground. You can use your pistol to defend yourself from enemies. Second Chance ends after 10 seconds or if you take a single hit from the enemy, and in both cases, you will die.
Pro Ability: If you have Second Chance Pro equipped you can survive a little longer than normal. Teammates can also revive you - even players that don't have Second Chance. You can see a white REVIVE tag above a player that can be revived.
Hacker | Hacker Pro
Ability: Allows you to see enemy explosives, equipment and Tactical Insertions. This highlights them with a red color like SitRep from Modern Warfare 2.
Pro Ability: This is one of the most interesting additions to the whole Black Ops perks list. Hacker Pro actually allows you to sabotage enemy Care Packages and also turn enemy equipment friendly. This also makes you invisible to Motion Sensors.
Ok finally the last slot. So which one do you guys prefer? Personally i like ninja pro for louder enemy footsteps. this is good for Hardcore and SnD. Especially if you have a good set of headphones. If im playing something else i like to use hacker pro. mainly because i can see claymores and the pro version you cant be detected by motion sensors which is really helpful.