Looking at it both the archetypes replace Trap Sense, a skill that the U.Barb doesn't have. The U.Barb gets Danger Sense instead. Not sure if there is an errata somewhere that makes Trap Sense and Danger Sense equivalent.
Well, I don't quite feel up to looking for one. (Danger sense seems to be just a slightly improved version of trap sense) but, Just to save on the hassle, I'll go with a "chained" Ulfen barbarian.
Regarding your question, emphasis mine:
Danger Sense (Ex): At 3rd level, a barbarian gains a +1 bonus on Reflex saves to avoid traps and a +1 dodge bonus to AC against attacks by traps. In addition, she gains a +1 bonus on Perception checks to avoid being surprised by a foe. These bonuses increase by 1 every 3 levels thereafter (to a maximum of +6 at 18th level). This ability counts as trap sense for any feat or class prerequisite, and can be replaced by any archetype class feature that replaces trap sense. The bonuses gained from this ability stack with those gained from trap sense (if the barbarian has trap sense from another class).
