Regarding the Samyang/Rokinon 14, I have one that I messed with on my a99 and it's pretty darn good. Impressively sharp. It suffers from barrel distortion, but that can be dealt with in post.
On the somewhat amusing side, Roger C. from Lensrentals added this when describing the lens: "I will note, this is held together inside with plastic, glue, and small screws. You won’t be using it for years." Still, at only a few hundred bucks, not a terrible buy if one needs something on the ultra-wide side.