I'm not personally excited about any of these potential lenses. It's not the focal lengths or apertures, but that sigma does not in any way get me excited. I've owned several sigma lenses including 8mm fisheye, 10-20mm, 18-200mm, 120-400mm and 300mm f2.8. None of them were remarkable to me in IQ or performance or worth the discounted price compared to their canon counterparts. IMO it's always worth the extra $$ for Canon glass...
I have used both Canon and Sigma 35 1.4; Sigma is noticeably better without the need for pixel peeping. The sigma 50 1.4 also compares very well to the Canon 50L from experience. You just have to pick the right lens range with Sigma
Arize...I agree. I own only the original Sigma 50mm f/1.4 (the ONLY Sigma lens that I would consider owning before the Art series and an apparent "new-leaf" transition of the company), and the new Art 35mm f/1.4 lens. Mine are both great lenses. I think it is fair to say that Sigma lens releases should be looked forward to, as all of their recent offerings have been impressive. I do think the rumored price on the new 50mm seems high, but I am excited to read the tests to see if it truly is an "Otus-type" performer. For now, it seems that this company has changed its ways and any new offerings are worth looking into, at least for this photographer. The results that I get from my 35mm are truly in the "WOW" area of the performance spectrum!