I have played Machrie (pre updates), Castle and Rosemount , all very enjoyable courses but I would not rush to play Castle off season , it's longish anyway and on loamy soil so may not be at it's most enjoyable in wet conditions.
Personally I've played 30 of the courses and enjoyed them all, always found good golf courses enjoyable and not particularly bothered about the rank order or the fact that a few other equally good courses may not be on the list. It's a useful list of courses which most golfers will thoroughly enjoy though the excercise may have the unfortunate side effect of putting up the prices.