Robert - I have been round both courses recently and it is a shame to have to choose! I think the received wisdom is that the New course is harder, mostly because it is longer (which again is at least in part a function of the Old course having quite a few short par fours, some of which are the best holes on the course).
The holes I like best are the 7th on the Old course ( a horrible blind drive, but magical once you get over the brow); the 10th - probably the most photographed - with the high elevated teed; the 11th - fabulous short par 4, sure to find you out if you are at all wobbly from 100 yards in and the 12th, with the lovely "pearl necklace" of bunkers strong diagonally across the hole.
On the New course, the fourth and the fifth and the ninth are favourites. There are some quite challenging "sleeper" holes, like the 8th and 16th which I often forget when trying to remember the course. I think the 18th on the New course is regarded by some of the locals as being a disappointing finish, but I agree that there is not much to criticise in the rest.
Not sure when last you were there, but they are busy renovating the clubhouse - the visitor's change-room is vastly improved!
The secretary and greenkeeper have both changed recently, so change is afoot - but the one constant remains the caddy group who, in my experience, are extremely accomplished, and pleasantly idiosyncratic!