I like the Samyang from the stand point of edge to edge sharpness at reasonable apertures. Because of low coma, it was very suitable for far field work ( astro-photography / tele-landscape ) and not as nice as the Tak 1.8/85 for portraiture. But as a modern lens, I think the Samyang outperforms the Tak in terms of the nisen-bokeh and other aspects where 40 year old glass just can't compete. This is from the s-m-c Tak 1.8/85 @ 1.8 for comparison
Any lens like this is a compromise, and they two are very different lenses. The Samyang is a great lens for the price, especially when the Tak is more money and not necessarily better depending on the work being done with it.