I will post my thoughts on 8 and 9 together.
The eighth at Whitinsville is a short par-4 doglegging left, the only hole on the course that feels just slightly awkward to me. Actually, it would have been a good companion for The Dunes #7, it's sort of a similar hole. The tee shot is back over the valley you hit across at the par-3 7th, and only a good drive will get up the hill far enough to get a good view of the green.
The eighth at The Dunes has always been the most talked about hole on the course. Like the 3rd hole, the fairway is interrupted just past the driving zone, but here the green is in a bowl atop a good-sized hill, and it would be in reach if only you could keep all the trees down the left side of the hole out of play ... but from a practical standpoint, if you're going for the green, you have to risk the possibility of hitting a tree and making a big number. Most people therefore play it conservatively. The only thing I have against the hole is that short hitters may not be able to get clear of the trees with two reasonable shots up the right ... that's pretty harsh! But it's an easy winner in this match.
The ninth hole is also an easy win, this time for Whitinsville. The 9th at Whitinsville was one of three holes Donald Ross chose to illustrate for George Thomas in his book, GOLF ARCHITECTURE IN AMERICA. The topography is spectacular, as you play your tee shot over the edge of a beautiful wetland pond. The landing area for the tee shot is at the end of a bluff about 200 yards from the green, which you approach diagonally ... if you can hit the tee shot far enough from the left tee, or far enough right from the back tee, you carry off the plateau and down the hill to a lower bit of fairway, which puts the green much closer. It's a great par-4.
The ninth at The Dunes is indeed a fine par-4, as Terry mentions ... almost as difficult a hole as Whitinsville's, because the raised green is very well defended by a bunker front right-center, and the fairway is none too wide. It's probably the best par-4 of the bunch, just too bad it's up against one of my favorite holes in golf here.
Someone earlier commented on "the sum being greater than the parts" and I do feel that's true of The Dunes. There are not many courses in America which present a better low-key atmosphere for golf, with the tiny clubhouse and the large patio and the walk-in-the-woods feel of the course. It feels like a private estate course, which in some respects is how it started. If ambiance had counted for anything in this match, it might have been enough to change my winner.
By the same token, it was interesting to see Anthony's take on the atmosphere at Whitinsville. I have always been an interloper there, but it does have the right "townie" atmosphere for a small town nine hole gem ... it's anything but posh, but the members are very proud of it. The key for me is that it is just a beautiful piece of land for golf, and there is a bit more elbow room for the routing to use the topography than at The Dunes, which I would guess is between 10 and 20 acres smaller, and sometimes feels a bit crowded together. [Actually, I need to do that comparison on Google Earth when I have time. Ross was a master at routing, so Whitinsville may be more compact than I realize.]
Bottom line, these are two wonderful nine hole courses ... by my count the two best America has to offer. In fact, there are not many courses in America among America's top 50 where the inferior nine would be better than either of these. Fans of one course or the other tend to discount the possibility that there could be another nine holer of equal merit, but they are dead wrong. I would encourage everyone who has the chance to seek out both courses.
I know I've promised to do an "architectural" comparison of the two courses also, and I will try to get to it later this week, assuming I have a decent internet connection in NZ [which is very iffy in the small town where we are working]. If I'm offline, I'll be busy trying to put the finishing touches on a course that might be better than these (!). I'll check back when I can.