Niall,
Here's my perspective. I like to think I'm an average US tourist golfer. First, I don't really believe in ranking or rating couses. Who am I to say what the "best" courses are, or why one course is better than the other. However, I do have my personal likes and dislikes, the courses I've enjoyed and those I haven't (among the 25 or so Scottish courses I've played), and I share my opinions with others.
I finally got on the Old Course two years ago, and am glad I did. Is it a great course? I don't know. We had fun, but I've done it and I wouldn't go back. Now I know, first hand, what it's about. I'm certain it must be an great course to the sophisticated golfer, but I like to see where I'm going, for the most part. I also played the New and the Jubilee. I liked the latter a lot and would play it again, but not the New. Niall, which St. Andrews courses would the locals rank as 1 and 2, with the Old being third, in your view?
Cruden Bay. I've played it twice and loved it both times. Why? The landscape and the course, combined. We've got nothing remotely like that golf course landscape it the States (that I know of). Maybe that's the turn-on. It was just lots of fun. You're probably right. It's just a holiday course. But I'll take the holiday. It tested me plenty, but not in an overwhelming way. What would the scratch golfer think of the course? You'll have to go to someone else for that opinion.
Royal Dornoch. We played one round on Nairn one day and then two on Dornoch the next. I couldn't play Dornoch "every day," but I could Nairn. Dornoch was too difficult for me (on a very windy day). Yet, if you pressed me, I'd have to say I thought Dornoch to be a far superior course, and I'd definitely like to play it again. The difference being, again, the course combined with the land. The Ross connection at Dornoch was marginal for me, even though I belong to a Ross course club here at home. It's not like he was the "architect" at Dornoch. On the other hand, our group did have fun posing for a photo in front of Ross's family home.
Prestwick and Turnberry, the latter possibly my favorite Scottish course (of the one's I've played, obviously) are two other courses at the top of my list. Carnoustie, Muirfield and Royal Troon, the latter allowed exceptions for some holes, are at the bottom (the bottom of a list of very fine, well-regarded courses, mind you).
The common thread that distinguishes my personal favorites from the others is the land. My favorites are all so very different from my experience in the States, while the less favorites are not. Does this make my favorites better courses? Well, maybe not in the pure golf sense, whatever that is? I do know, however, which courses I'll recommend my US friends play when they visit Scotland. For me it's not so much as a "ratings" issue as a "have fun golfing issue." Maybe that's what some of us Yanks translate into "best."