Did some digging for information on what certain stats do, some of the info was clear, other info is a bit more open to interpretation. I put it together in an easier to figure out format.

Check marine_skills.cfg in "\alien swarm\swarm\cfg" to look at some of this info yourself.

Shared Skills

Health Bonus

80 health base, +15 health/point

Melee Damage Bonus

30 Base dmg, +6 Melee dmg/point

10 base force, +1 force per point

+0.1 speed per point, 1 base speed

*I think force is probably knockback and speed probably increases melee attack rate.

Speed Bonus

+10 Movement speed per point, 290 base movement speed

Reload Speed Bonus

Increases size of fast reload area by 5% per point

Reduces reload speed by 14% per point

Base reload speed is +40%, with full Reload it is -30%

*This means by default you have 1.4x reload speed, but with full reloading you have 0.7x reload speed

Damage

Assault Rifle: 5 dmg base, +1 dmg/point

Prototype Assault Rifle: 5 dmg base, +1 dmg/point

Pump Action-Shotgun: 25 dmg/pellet (175 total), +2 dmg/pellet (14 total), 7 pellets

Precision Rail Rifle: 75 dmg base, +10 dmg/point

Flamethrower: 2 dmg base. +0.5 dmg/point

Twin Pistols: 14 dmg, +2 dmg/point

Personal Defense Weapon (PDW): 7 dmg, +1 dmg/point

Marksman Rifle: 65 dmg, +10 dmg/point

Explosives Bonus

Grenade AoE (most grenades): 280 AoE, +20 AoE/point

Assualt Rifle Grenade: 80 dmg base, +10 dmg/point

Vindicator Incendiary Grenade: 80 dmg base, +10 dmg/point

Frag Grenade (per cluster): 80 dmg base, +10 dmg/point

Freeze Grenade: 210 AoE, no increanse, 3.0s freeze, +0.3s/point

Grenade Clusters: 0 base, +1/point

*I'm still figuring this one out

*clusters seem to be a point system used to determine how many of a grenade are thrown, for example trip mines is 2 mines at 2 explosives and 3 mines at 4 explosives

Officer Skills

Leadership:

+3% chance to deal double damage per point, applies individually to each pellet

+6% chance to reduce damage by half

Vindicator Damage

15 dmg/pellet base (105 total), +2 dmg/pellet/point (14 total), 7 pellets

Specialist Skills

Autogun Damage

Autogun Damage: 7 dmg base, +1 dmg/point

Minigun Damage: 7 dmg base, +1 dmg/point

Piercing Bullets

20% chance for bullets to pierce per point

Piercing bullet does damage and continues through alien

Medic Skills

Healing

Healing Beacon: 4 beacons base, +1 beacon/point, 25 healing base, +8 healing per point, AoE may increase with healing points

Healing gun: 40 charges base, +10 charges/point, 5 healing/charge base, +1 healing/charge per point (heals every 0.33s)

Self Medkit base healing 50, +5 healing per point, only increases self medkit for medic

*self medkit claims it increases from 50 to 80, but math only works out to 75 healing with 5 points

Infestation Curing

Reduces infestation by length by 25% per point

Combat Drugs

Adrenaline lasts for 5 game seconds base (~11 actual seconds), increases by 0.8 game seconds per point (~1.76 actual seconds)

*what this mean is if you turn on adrenaline with no medic it will last about 11 seconds while 5 seconds worth of play passes.

*note the is some discrepency between the claimed values, 5s(11s)-11s(21S) and the way the math works out

Tech Skills

Scanner

650 base, +150 range per point

*note config files say max range is susposed to be 1350, which would be +250 per point, this is either an error or 3 points in scanner is actually interpreted as 5 points

Engineering

Claims base speed of 60% and increases to 210%

Base weld 0.8, 0.5 per point (uses 1.0 if no tech is present)

Base turret 1.0, 0.25 per point

*this is pretty hard to interpret, I just know with vegas around it goes very fast