Played both, like both, but Vengeance is better(though it pains me I can't say rage).
It's better at defense and at successfully rooting enemies. Charge(1st root) -> Ravage(2nd root)->Saber throw with root from utility(4th)->Impale autocrit from vindicator set->shatter->Ravage(5th). This is, clearly, hypothetical, but most of the times, attacked player will panic and use breaker.
Also, Vengeance has a nice and simple flow, compared to Rage, where you have to hit certain abilities to obtain procs and knockbacks and stuns often screw up your rotation. Damage wise, Rage IS superior, considerably so, I would say, and if you focus targets well with other players I would say it can be more effective than vengeance. But being cc-ed leaves a lot of open windows where you lose time(=therefore, damage), and Vengeance makes up in that.
I think people should test both more and explore, and then post feedback regularly, based on results .