In pvp, open wounds kicks crushing blow's butt. The reverse is true for pvm.
in pvp cb takes away 1/10th of a player's remaining life. So, as you go along in a duel, cb does less and less dmg. If you're dueling bvb against another barb with 5k life and your first hit triggers cb, you will have done 500 dmg (4.5k remaining) + whatever weapon dmg minus any pvp penalties to that. Next, 450 dmg, 4.05k remaining, 405 dmg, etc. As you can see, cb does fairly respectable pvp dmg for high life opponents. The problem against high life opponents is high def. For cb to be effective against high def opponents, you'd want it to be triggered often. That doesn't happen. Also, cb is resisted by pdr.
in pvp ow does 1/4 its usual dmg which is based on a players clvl. There is no decrease in dmg output as the opponent's life closes in on zero. Since I used the example on high def/life opponents, I'll continue that. dmg per second for clvl 85 = 61 dmg/sec over 8 seconds. In bvb dueling, it isn't unreasonable for 8 seconds to go by without a hit, so you're causing dmg to your opponents after the fact. The dmg totals to 480 dmg over 8 seconds of unresistable torture.
with cb, by the time you get the player's life below 4k it does less dmg than ow. And the situation only gets worse the closer to zero you get.
Now, in pvm cb rules the house against high life monsters, because they are much easier to hit and often don't have the penalties that come with pvp. Not to mention their life often ranges in the 10-20k area, so significantly more dmg will be taken with cb than ow as only cb scales with life.