depends on whichever one you have higher ar with. ignore target's defense mod doesn't work on bosses. in both cases, when i tried, i get around 30-40% chance to hit on both zeal and ww because i rarely use ar eq nor raise zeal/ww to 20 for skill ar. also, for both chars, dex is never above 120 either.
 reading what i just wrote: barbs have been nerfed down so close to pally's it sickens me.
Versus act bosses like Baal, it's not a matter of damage, but a matter of how often you can trigger a crushing blow. The problem with WW and Baal is that you constantly run out of mana. I'm not a friend of drinking potions all the time, so that might be a problem just for me.
My IK barb (40% CB from IK maul) needs far longer to kill Baal than my fana-zeal paladin (15% CB from Goreriders). The barb normally whirls if he has enough mana (more hits -> more CB), else he uses conc, while my paladin uses smite (always hits) to bring him down to a sliver (making short switches to zeal to fill up mana) and then finishes him off with zeal.