Yeah I am a little confused about that actually. Like if Yorcia Skirmish is a zone... or the same zones as the other and different gameplay gimmick?
I *think* what I want to do is Rala, because I would like to get the Kumbhakarna axe... at least from what I can tell that is how I get it. Also would like to obtain some of the like... Acro and Taeon gear.
Yorcia Alluvion Skirmish has gimmicks that can let you easily solo the event without shouting for a group of 6 good players but the Rala and cirdas Alluvion force you to be a super nerd badass pro to solo it or shout for a group. (sadly pointless in 2016 since no one would join)
Yorcia also drops mellidopt wings which can be exchanged for weapons and armor of your choice while the other zones don't drop them, they only drop specific weapons from specific NMs that can be near impossible/luck based to find.