Cary:
How bout you step out on a limb and declare which of the two you preferred?
I have not played Aronimink since the work by Ron Prichard so my comments are more from a dated positoin.
I have played Plainfield since the work of Hanse / Bahto and frankly see the course as being one of my personal top 50 layouts in the nation.
The measurement of Plainfield comes from a variety of ingredients ...
1). Superb setting -- the flow and naturalness of the property is simply first rate stuff.
2). The juxtapostion of the holes -- you are constantly kept off any particular pattern. When you get a combination like the par-4 10th (save for the silly pond), the delicious par-3 11th (with its false front) and the spectacular par-5 12th with its serpent like creek and unique rib cage that splits the two sections of the green, you can feel the qualities of a well done layout that never bores you.
3). The par-3's -- with the lone exception being the overal difficult 14th are truly enjoyable.
4). The green contours are well done and place an emphasis on fine approaches and deft control of the blade.
5). The lone weakness -- the lackluster 18th. It was the 16th for the early days but I have never really thought much about how the round comes to an end at Plainfield.
6). The opening hole at Plainfield is one Jersey's best and IMHO as good as the starting hole at PV. Well done restoration has now brought back into play the left fairway bunker and the demand on the tee shot grows for the better player now.