Tim
I guess I have "jumped into the fire" so here goes. Remember that an opinion is just one persons thought.
A. I get the same "fear factor" driving through the gate.
B. I get the same feeling from the facilities.
C. Both courses were designed by "Amateur Architects" who did not do many other courses.
D. "Blasting away" from the tee boxes is not a good idea if scoring is desired.
E. The speed of the greens require an approach putt from the proper location.
F. The greens seem to blend into the fairways in many instances.
G. Both have short holes requiring club selection from the tee to the proper approach position and precise shotmaking from the fairway.
H. Both have long holes requiring length AND position.
I. Both are in Pennsylvania. I am prejudiced in this vein, being a native "Pennsyltuckian"
J. The green complexex are IMVHO are somewhat similar in that they both have somewhat large greens on some holes that play small. The greens have wonderful undulations and slopes with great speed, yet allow for a ground approach if needed (Some, not all).
K. Both courses have storied pasts, hosting many major and minor championships and stories and legends abound as you proceed around the courses. It helps to have a caddy or a member with you that knows the history and can tell a good story.
L. Both are easy to walk. The fairways are rolling and present lies of all kinds.
At this point I must add that the original intent was quite different in the design strategy. Fownes wanted a very penal course. In reviewing Cornish and Whitten's, "The Golf Course" I am reminded of the fact that the clay base of Oakmont did not allow for deep bunkers, except a few, and therefore designed the infamous rakes. I never saw or played the course with these bunkers, so I refrain from comment. The bunkers must have been awfully difficult to negotiate. A very different strategy was employed in the design of Merion. I guess that time has brought them more closely together.
Oakmont was started in Approximately 1902 and Merion was started nine or ten years later. I think it is highly probable that Wilson visited Oakmont and discussed ideas with Fownes and perhaps Fownes took some ideas for revisions back with him. This is a pure guess, but given the consultaion which probably was more prevalent at that time, seems to make sense.
Merion doesn't provoke the same "fear factor" as Oakmont to me, but it does invoke the same feeling that I better bring my "A" game and head when doing battle with those girls.
I will elaborate more later when I can think of it.