I'll try to make this clear and brief.
I have a 5dmkii that I shoot with 99% of the time.
My favorite lens is my 85Lii (3 years now), I'd sell my kidney to keep it. I'd love a wider version of that lens.
Until recently, I had a Canon 28mm f1.8 and 50mm f1.4 as well. I'm considering replacing them. I was thinking about replacing the Canon 28mm, but getting a Sigma 50mm f1.4 instead of the Canon 50mm. I had a Sigma 30 years back and LOVED that lens, so I'd love the same quality in a 50mm. The Canon 50mm f1.4 was decent, but i found the bokeh busy sometimes, and the wide-open haze and low contrast annoying, and wonder if the Sigma would make me happy (i think it would). I really liked the Canon 50 above f2.0
However, as I was sitting down and looking at the money I've saved up to buy another 28mm and 50mm (whether canon or sigma), I found that I might be closer to a used 35L than I realized. So here is my situation:
-I like the 50mm as a general, one-lens walk around kit with my 5d. Or if I took a zoom, I could throw the 50 in the bag just for fun, if I want DOF, or a not-wide-not-tight low light lens.
-The 28mm was a good prime, and irreplaceable when I needed it. I found it sharper and better in CA than rumor says it is. I didn't use it as much as the 50mm though. I had it mainly because I wasn't happy with the 50mm being my widest low-light lens, so it was mostly a supplement to my most useful prime, my 50.
-I've never had a 35mm prime. I wonder if it's close enough to 50mm to satisfy that need, but also wide enough to satisfy my need to have a fast prime wider than 50mm, i.e. my 28mm. I have other wider lenses for things like landscapes and architecture shots.
So the question is, is it worth giving up a 50mm+28mm+some money to get a 35L? How bad is the 35L CA (I don't find my 85L or my previous 28f1.8 too annoying)? Is the 35 a good "one-lens" replacement for my 28+50? Maybe a 35L and then a 50mm f1.8 a little later so I have a tiny lens I can throw in the bag as a "just in case prime" when taking one zoom for lazy zoo/beach/snapshot pictures?