OK, Donal, let's start with 6 at Cruden Bay because it's one Anthony knows well, I think we can assume.
It has an intimidating drive, with real advantages to keeping it left, despite that being where the worst trouble is. Then, having hit a good drive, there's the temptation to go for it. Even if you aren't tempted to go for the green (and the way it's tucked away and angled makes it difficult to hit and hold and the penalty for falling short is severe), is it worth trying to carry the burn and have a relatively simple chip up the green? If you lay up you really want to do so close to the water to give a better angle to that green, which itself isn't easy.
12 at KB may be more spectacular but doesn't strike me as having a particularly interesting tee shot or, for those who are going to lay up (and I think that's most of us) I don't think there's that much to the lay up. It's a good hole but not, in my book, as interesting to play as 6 at CB.
9 at NBWL has a really, really interesting challenge off the tee. Drive between the centre line bunker and the OOB and have the advantage of being closer to the green AND having a better line, or bail out right. Then there's the second shot. From the left (having taken on the dangerous drive, you can go for it, because anything short will be ok. From the right, going for it becomes a really difficult shot. Even the lay up isn't straightforward, as getting both line and length reasonably right is important. The green has a steep slope asd is really easy to 3 putt, particularly if your approach was on the safe side and is past the flag. Of course, if you're short of the flag there's the danger that you might have rolled back down the fairway.
I think Simon described what makes 11 at NBWL a great hole. Can we ask Anthony why he prefers 12 at KB now?