Several years ago, I descended both routes on the same day. I went up and back down the MR, took a short break, and then went up the MR a second time. I was concerned about making a route-finding mistake in the dark while exhausted, so I descended the main trail. It took a lot longer than the MR would have taken, but there was less chance falling or getting lost in the dark. If I did another double, I would stick to the MR. However, you can always make that decision on the summit.
