I had the Nikkor 85mm f2 AIS and was pretty happy with it. It has the advantage of being a very compact lens.
I then got the opportunity to cheaply pick up a Nikkor 85mm f1.8 which was a K (pre-AI) model which had been factory AI converted. While it's considerably bulkier, I think it's a superior lens in terms of performance (and obviously half a stop faster). This is also largely borne out by independent tests I've read. I then sold the f2 lens.
I always fancied the f1.4 Nikkor but have never been able to justify the cost. Now I have the f1.8 I'm very happy with it and don't feel the same need. Have never used one, nor the Samyang, so can't comment on either of them really.
85mm is one of my favourite focal lengths - a must have for me.