I've done the Prow a quite a number of years ago when it was 85% equiped with fixed pins (intentionally, by Paul Ross, as a practice aid route). I understand that now most of those are gone. I've been back to it twice since then - once for photographing friends and once to repeat it. I've often considered but never got around to doing the Mordor, but I did try to get beta on it.
There's quite a difference in difficulty between the two, with the Prow being A2/C2 at most, and only in a few spots. The Mordor was A4 at one time. I don't know if it's gone clean yet, and I'm certain the cracks are pretty beat out, but it will still be harder - there was just bunches more hard aid on it than the Prow. There's the expando flake and thin crack on the first pitch (now 5.12-something), the bat hook traverse (now with multiple chicken bolts but still with flared out holes) followed by the one-time RURP and tied-off blade crack (additional chicken bolts) on the second pitch. The third started with more thin nailing. I don't know the condition of these now nor how well cam hooks, offset aliens, z-friends, Lowe balls, and other modern trinkets would work.
The Prow on the other hand is basically very straight-forward cracks that range from thin fingers to small hands with maybe a hook here and a bolt there. A number of the aid pitches do go free at less than 5.11. At one time the first pitch was a mixture of rivets and bolts up a steep slab, but that was chopped some time ago. There's a 5.7-ish alternate start a little to the left of the original.
Which is better? I dunno. The Prow always struck me as the more aesthetic line, but the Mordor is more striking. Depends how hard you want your aid. As always, YMMV.