I have the Samyang also, and really like it. The projection of the Samyang is different from Nikon 10.5 and just about any other fisheye. I don't know the math behind it, but with the Samyang, the distortion at the image edges is somehow not so extreme and the images are really usable.
So don't just compare them on price.. I'd pick the Samyang.
So don't just compare them on price.. I'd pick the Samyang.