Quote
L4D is definitely better. You can play as zombies, there are mutations every week...
Well you can dowbload mutators for killing floor to play as specimen.
Here is a list of specimens:

Scrake

gore fast

bloat

cloat

husk

fleshpound

night crawler

siren

Stalker

patricarch (final boss)
Weapons:

m14

cross bow

Lever action rifle

9mm

handcannon

Scar

mp7

knife

bullup

ak-47

machete

axe

pipe bomb

grenades

L.A.W

dual 9mms

dual handcannons

Shot gun

Hunting shotgun

AA12

Flame thrower

m79 grenade launcher

m32 grenade launcher
Gamemodes:

Survival

Snadbox