massacre 110ap is cheaper and constant
but berserking is a little better over time

massacre rduces armor
that reduction stacks as massacre procs often enough to refresh itself.
depending which class, benefits from massacre more.
but massacre is cocaine for dual wielders who dont get output boost from armor.

i've put berserking on my rogue mh
pali and warrior both with flat 110ap enchant

as i recall, theorcrafting on wowhead says berserking is about 140dps average. only worthwhile for a weapon your not going to replace the next week though.