This is an argumentative thread isn't it? BTW, is it fair to compare a 35mm lens (Sigma) to a 55mm lens?
Isn't it expected that wider FL primes tend to "fall short" of longer FLs in terms of bokeh ? For instance, would a Nikon 24/1.4G ever be expected to have more favorable/smooth bokeh than a Nikon 85/1.4G ?
I think the purpose of each respective lens is different. I don't use 50-60mm FLs much, therefore I've even considered selling my 50/1.8G because I never use it. I use the Sigma 35mm much more -- as I used the 35L more than my 50mm when I shot Canon.
That being said, I certainly hope the OTUS is the more refined, superior lens. Price aside, they've been in the business MUCH longer than Sigma has and German optics are akin to Japanese automotive engineering perfection. I think the Sigma will be a great, great, great lens and if it's completely better than my Sigma 35 -- and I can trade up completely free of charge -- I'll stick with my 35mm.
I almost bought Nikon's 35/1.4 but concluded that the Sigma was actually the better lens -- build quality, AF, bokeh, and sharpness of course. The problem I see is that of the elitist attitude ---> how many of us are keeping a lens for the next 40 years? 30 years? 20 years -- perhaps. Technology has evolved and as prices have dropped, so has the method in which we consume products. Precious metals, firearms, artwork -- these are all better investments surely. I'm not into photography for investment purposes. So therefore, I'll buy what I need. Price can sometimes be prohibitive. I could sell my new 70-200VRII, 24-70/2.8, 24-120/4.0VR, 16-35VR -- and probably be able to afford the OTUS. Personally, I would rather not. Especially since 50-60mm FLs are not my cup 'o tea.