Beserker VS GuardianFollow

Please temper my answer with a grain of salt since I don't play a tank... but I do play a warden so I have to keep them standing!

At any rate, guardians are the mainstay of the tanking archtype. They have the best taunts and so can maintain aggro when no one else can. They also have the largest health pool so they tend to be able to take the most damage.

Zerkers are kind of like a hybrid plate-tank being part tank and part DPS. Their damage output is higher but they can't MT or single tank as many of the end-game high-end instances as a guardian can.

For a while, I was raiding courts in T6 and we used to keep both a guard and a zerker along with 3 healers (mystic, warden & temp) in the MT group. The two of them would switch off MT depending on which name we were on.

Since I regularly group with both and as MH in the MT group on a lot of my guild's raids, I can tell you that from my point of view when well played there is little difference between them but my money still goes on the guardian every time!

Our guild's main tank is a Zerker, my gaurdian is off tank. Given that his gear is twice as good as mine, he doe a fine job. Zerks also have the ability to increase hate gain everytime he gets hit. This can out agro a gaurdian's hate gain on most melee mobs. I've put my AAs into DPS and still can't touch the zerker's DPS in a raid. He averages in the 700s on a raid where I'm lucky to pull in half that. Maybe once my gear catches up, I'll start taking over. Until, our zerk it MT.