We've done "luxury" (Crystal and Silversea) and prefer Cunard. For about a million reasons, actually, but among them are elegant surroundings, consistently well-prepared food, live music (no electric pianos, thank you very much), some great bars, and first-class lectures. Service is on a par with those others, in the Grills, anyway. It may not be "luxury," meaning it's not all-inclusive and the ships are larger, but it sure is nice.