I'd pick 12L.

The first time I flew an odd middle with someone I didn't know, I absolutely hated it. The partition doesn't go up far enough to avoid getting some incidental face to face, especially if you are a bit tall. By now I have gotten over it, but I remember how intensely I disliked it at first, so even if I can get through a flight without feeling awkward about it now, I would still rather not .