I had both. Loved them. The Plena made for fantastic images, but since I do mainly portraits, having them both seemed a little redundant. I kept the 85, because I shoot mainly 85/35. Before I switched to that combination, I had the 50 1.2 and Plena. I found 35/85 to be more useful for my specific shooting needs.
I agree with the folks above. I'd think about what I was going to pair it with. If I had the 35, I'd definitely go with the 85.
My vote is Plena. Id go 50mm 1.2 with Plena. Depending on how/what you're shooting. If its in doors, 85mm may make more sense but if not, the 135mm is one of Nikon's most praised lenses ever. Optically eliminates vignetting, LoCa, chromatic aberration, unmatched bokeh... I could go on.
Same fo me, it's definitely 135mm and therefore the Plena.
But of course, it depends very much on the application scenarios.
For me, that means outdoor use, and even back in the days of my Canon F-1 in the 1980s, I preferd the 135mm focal length, even though I had a Canon FD 85/1.2 L and only the FD 135/2.8, which was a revolutionary 85mm lens at the time.
Since I have permanently attached the FD 85/1.2 L with an FD to Z adapter, that's enough for me in situations where I need 85/1.2.
The Plena is something special to me, not just a professional tool for the highest demands, but a work of art in optical engineering.
