Proximity alarm - Automatic warning when an enemy is nearby
2ed - Faster chime
3ed - Fastest chime
Stealth Endurance - Faster transition in and out of stealth
2ed - No shadow in stealth
3ed - Basically cuts stealth energy use in half
Aim enhance - Decreases weapon recoil when aiming down sights
2ed - Less camera movement from external sources (falling/being shot)
3ed - Faster movement while aiming
Armor Enhance - Reduces drain speed of energy in Armor mode
2ed - Move faster while using armor mode
3ed - Immune to armor jamming
Covert Ops - Suppresses the sound of footsteps
2ed - Immune to ceph gunship
3ed - Louder enemy footstep
Side Pack - Allows an additional magazine of primary ammunition to be carried
2ed - gives an extra mag for your secondary weapon
3ed - gives extra attachment ammo
Air Stomp - Perform a powerful downwards attack when in the air
2ed - Additional control while airborne
3ed - Less recovery time after air stomp
Cloak Tracker - Identifies when enemies enter Stealth mode nearby
2ed - Increased enemy cloak visibility
3ed - Max enemy cloak visibility
Weapon Pro - Faster weapon reloading
2ed - Faster ADS
3ed - Faster weapon switch
From http://crysis2news.blogspot.com/