I love the two Zeiss lenses I use - 18 and 85mm, but I find nothing "magical" about them. I will say they have a different "look" in a small way to them - more saturated perhaps than other lenses, but I think this is more a personal observation than anything I can put down in a graph or chart for any of you. I just like the look of the images I get with them.
The Samyang lenses are excellent, especially for the money. I looked real close at the 14 - F2.8 before I bought the Zeiss 18mm, and while in terms of sharpness and contrast the Samyang holds it own, the distortion is usually worse I find. yes, 14mm vs 18mm is a bit of an apple vs orange comparison, but still I stand by that comment overall.
While I really love my Zeiss 85mm F1.4, if somebody where on a budget, I would not hesitate to recommend the Samyang 85mm F1.4 Zeiss lenses are tough, and from first hand use, they will take more punishment out there than just about any other lens save for some of the older manual focus nikkors. Samyand lenses are not as tough as Zeiss lenses, but they are still, I think, very well built. The 8mm fisheye is awesome on Dx sensor cameras, there is nothing out thee for the money, IMO, that can touch it.
If you are in a rough enviroment, that is something to consider. One thing I have round out, first hand, form just getting my nikkor 24-70 back form Nikon repair for service, is these new auto focus and vibration reduce and/or image stabilized lenses have a lot more to go wrong with them if they take hit. Depends on your needs, the places you are shooting, etc. I suspect for most weddings, the 24-70 zoom, Nikon or Canon, is a perfect lens for most situations. But if you are rock climbing, i would suggest you consider a Zeiss prime, just in case. ( Maybe a Zeiss prime for weddings if you become a staff photographer too for "Bridezillas" too. )