Well, I belive that salmonids that require more fat reserves because they spend a longer time in fresh water before spawning are the best tasting. Spring chinook, summer steelhead, and sockeye have by far more fat content and will be so oily that you can not wash it off after filleting one.
I have eaten plenty of oregon spring chinook, copper river sockeye and chinook (other ak salmon too), and columbia river summer steelhead. I think Colunbia river summers from below Bonniville are by far my favorite.