I returned my sigma yesterday and got my 35L today. I was extremely happy the first 15minutes. The handling is right; the AF is substantially faster (maybe 30%?) and incredibly consistent; and the bokeh is beautiful.
Then came slight disappointment. On computer screen even without zooming there's very visible CA and purple fringing on some images. I think I'm seeing them because I know where to find them.
Sharpness wise the 35L is sharp enough at 1.4. Maybe Sigma is sharper but the 35L is sharp enough for my purposes.
I love the AF and handling of the 35L. Every shot so far is accurate. The CA is a bit annoying. Maybe this is the biggest limitation of this old lens. There's less vignetting than Sigma but I care less about this. I think the 35L is too expensive also. The Sigma is priced right. But its AF is a big disappointment, at least as far as my copy is concerned.
I'm leaning towards keeping the 35L. There is quite a bit of work to remove CA in LR, but maybe I'll live with that.
Maybe I'm missing the point but I just remove CA with one button in LR. Removes enough of it to be a non issue for me at least.
With pictures taken at 2.8, one click on "remove CA" in LR will take care of most unwanted colored lines. Pictures taken below 2.8 need manual defringing with the dropper. Maybe I'm not doing it correctly. Any insights would be appreciated. That's just my observation from 3 hrs of owning it. Could be wrong.