kurzick = gothic
luxon = al bhed's great grandparents
I have a slightly different take
Luxon = Al Bhed
Kurzick = Centauri (from Babylon 5)...
Anyway, Luxon areas are far more aesthetically pleasing, however Kurzick armour looks sweet. Other plusses for Kurzicks are better henchies, easier travelling to the next area, and you get to fight Mantids which are the coolest looking enemies in Factions.