Rokinon 35f1.4 versus Sigma 30f1.4

If you can live with using live view (remember you'll have to punch in to 10x to get critical focus and then punch out to recompose--slow) and the awkward focal length, slightly too long for a normal lens, then the Rokinon won't let you down optically, though I wouldn't be surprised if the Sigma were sharper in the center. For corner performance and micro contrast and bokeh the Rokinon is quite good.

Personally, I can't compose and focus fast enough if I have to use live view for everything unless I'm shooting still life or landscape, so for me the lens is basically useless except for video. But it is one of my favorite lenses for video. Optically it is quite good and is beautiful on full frame. I have ignored it completely for stills but might install magic lantern and try using focus peaking and so I suppose it might be a decent investment if you plan to upgrade to full frame later. The 50mm f1.8 is also wonderful on full frame but a focal length I dislike for APS-C.