I'm torn between the zerker and the commando right now, mostly because I'm playing solo, which gets insanely difficult rather quickly. I find the turret helps divert some attention away from me, while at the same time helping get my second wind if I go down.
The zerker, on the other hand, has essentially an infinite health and ammo regen on a timer, which is handy for those long, long treks across the map with no ammo dump or health station in sight. The damage boost and reduction also help out a ton in boss fights, even though some require me to run away for a bit and pop it a second or even third time.
Still, having fun, loving the challenge of playing solo. The sense of accomplishment after finally taking out a tough boss is almost as satisfying as making your way through Dark Souls. Different games, I know, but it's been a long time since a shooter has given me this much of a challenge.
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