Matt,
I played Plainfield last month during the NJ Open. It was playing firm and fast in 95+* heat. Don't get me wrong, I really enjoyed the golf course but there were a few holes that I didn't care for.
I thought #4 was an odd short par 4. With the huge hill, I thought driver from the tee was the only option, as anything less than a 240-250 yard uphill tee shot would cause the ball to run back down the hill 50-70 yards leaving a long, blind uphill approach on a very short hole. And with driver off the tee, the slope of the fairway over the crest of the hill funnelled the majority of tee shots into the high right rough 40-70 yards from the green.
#8 has a big tree over the top of the hill on the right, at the end of the driver landing area that really makes the hole awkward. If the player is long enough and skilled enough to carry the crest of the hill on his drive, the ball can't be anywhere but in the left edge or left center of the fairway to hit the green in two. It is such a short par 5, that the tree is the only defense against a longer hitter. If you did hit the tee shot up top and on the right side, you now have to hit a short iron/wedge 2nd shot followed by the same club for the 3rd. I thought it was a cheap way to defend the hole. For me, it would play better if the tees were moved up, the tree removed, and have it play as an outstanding long par 4. The hole doesn't reward a great drive. I played with a couple guys that couldn't drive the ball up top, so to them, the tree would never really be an issue, because the hole would always be a 3 shotter, even though it is relatively short.
With firm conditions, I didn't care for the tee shots on both 17 & 18. 18 more so than 17. I understand that #18 was not originally the closing hole, but that doesn't change the fact that you have a right to left dogleg with a small pond on the corner with trees behind that, and then a fairway that slopes away from you. I hit my hybrid 2 iron over the trees on the inside of the dogleg, only to have the ball hit in the left side of the fairway and bound into the edge of the right rough. There were a couple of other options, but both of them weren't great either. Bomb driver somwhere farther up the hole to the left and hope for a good lie or lay back to 160-170 yards, leaving a long uphill approach to a difficult green. I don't like laying up to a long yardage on such a short hole. I would describe that hole as awkward to me.
As for Mountain Ridge, I'm not the only person I know who holds it in such high regard. There are several guys that played Mountain Ridge in the NJ Am a couple of years ago as well as in this year's Compher Cup who also played the NJ Open at Plainfield and they had similar views to mine regarding both courses. I jusy don't see the overwhelming superiority of Plainfield compared to Mountain Ridge.
As for Somerset Hills, the course is a blast to play, but modern technology has really hurt the course. For a good amateur player with top level driver distance, there really isn't a par 5 on the golf course that can't be reached with an iron, some even a mid-short iron. Except for a lack of distance, the course offers so many other great architectural features that it remains one of the higher ranked courses.