There are a lot of opinions re: white vs. red kings (ie. diet, genetic strain, condition, etc). The most recent 'scientific' explanation I've heard is that the white kings lack a gene which allows the meat to assimilate any red pigment of it's prey.

Most of the guys (myself included) I fish with always thought the whites seem to have a higher fat content... especially good for barbeque or smoking.

A guy I know, who's in his fifties, grew up working in a large fish market with his dad, a fishmonger. His dad would hold the white kings for his very best customers ... they felt especially lucky to have an opportunity to buy them.