Hi Bill,
I'm not exactly sure what it is, but I do prefer the Old to the New. There's not a great deal in it. In the "Who are you guys?" thread, I posted my top US courses and top UK courses and the New made it on that list. I think on the Old, I'm not a huge fan of the 1st hole and 18th holes, but apart from those two, it's 16 great holes IMO. The New has a lot of good holes on it too (and the 18th on the New is much better than on the Old), but it has a few holes that I'm not a big fan of.
On the New Course, I think 2, 4, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16 and 18 are great holes, but the others I'm not quite so keen on. Like I said it's close and I never feel cheated if the New is the course I'm playing. I do feel slightly better when it's the Old though.
The land the two courses are on is basically the same and they are very similar in many ways. They feel the same when you play them. Take 3 on the New though. That's probably my least favourite hole on the courses and it's because there's a bunker and a band of heather across the fairway at about 250-280 yards from the tee. That, with the shape of the fairway and the pace the ground runs in the summer means you have to lay back a bit from it, so you're pretty much always hitting a 200 yard shot to a green that has a false front, so it's hard to run it up. That all means I pretty much always play the hole the same way and I don't like that. If the bunker and heather covered half the fairway then I would think it a much better hole because you could take the chance of risking it to give yourself an easier second, but at a cost. As it is there's nothing to tempt you, so playing safe is all there is. All that said, I don't hate the hole. The green complex is interesting and the two bunkers either side of the green play havoc with your mind on the approach shot.