This is much the same as the 35L vs 35A debate..... If you want a sharper lens with harsher bokeh go with the Sigma Art Lenses... if you want an overall smoother rendered pic go with the Canon equivalent. Though the 35A is sharper (I owned it for a few months) the 35L rendered the better image to my eyes... Sharpness isn't everything.
I agree with your 35L vs 35A conclusion BUT honestly all this talk about the bokeh of the 50L being better seems like unfounded assumptions.
In every test I have seen the Sigma 50A outperforms the Canon 50L in bokeh. The Sigma lacks the aberrations and flaws, and business that the Canon shows while delivering the same punchy contrast in the background blur.
It's like somehow people have already decided that the Canon has better bokeh despite having evidence that seems to be to the contrary.
Well, that's an opinion of other photographers on this forum which is probably best kept to your self. Unless you want to single out someone specifically and start a flame war.
I have used a 50L for many years. Taken countless professional weddings and a number of landscapes with it.
I found for landscape work, there are sharper options, especially when stopped down. Professionals aren't particularly bothered is Sigma makes a slightly better optic than Canon... pros buy Canon for several reasons, they are generally built to a far higher standard. In 7 years of wedding photography I've never had an L lens fail on me. I abandoned Sigma several years ago due to their comparable fragility, heavy weight, poor flare control and inconsistent AF. I've owned 6 sigma EX lenses over the years and sold them all. 5 of them went back to Sigma due to poor reliability.
Sure Sigma may have made their new 50 and 35 to better specs...but I'm done with them as a brand, I won't trust my photographic business to their products anymore. I bought a 120-300 OS to see if they had improved and found all the old issues. So I re-sold that particular lens and I'm not even going to bother with the new 35 and 50...why? Because I've had 7 years + of sterling service from my Canon 50 and 35...so why introduce a new risk? I'm happy with the results I see and my photos and services are selling. Your mileage might vary.