Actually the Princess ship is larger and newer, Golden Princess versus Rhapsody of the Sea.
If the CEO of RCI did in fact say he "won't discount cruises to fill ships", that sounds like a good clue even if not literally true all the time. And clearly Princess has more inventory to fill in the Alaska market, so perhaps more incentive to test the elasticity of demand.
Basically I'm curious if there is any kind of pattern that can make bargain hunting a bit easier and more certain. My email and snail mail is inundated with alleged "great deals".