I'd go for the Arcane Barb. With the high AS on Calamity you will deplete your hatred faster and each attack ought to do less damage due to lower damage range on Calamity. Just my opinion. I found a Calamity today and I don't even think about using it.
You'll deplete hatred faster but regain it just as much faster. Which should result in a more or less equivalent final DPS in any fight lasting longer than a single hatred bar. Which is most tough fights.
The question is whether MoD provides +13% DPS.
Not really, cause most of your hatred regen actually comes from Companion, Healthglobes (Reapers and/or Blood Vengeance) and Preparation-Punishment or Vengeance
I would go with the Arcane Barb in Solo play and the Calamity in group play