These comparisons serve to reinforce my decision to just stick with the Canon lens.
I'd already reached that conclusion with other close comparisons I've seen elsewhere. I just don't see enough difference to justify the extra expense, added weight/size of the Sigma, which may or may not work with future EOS cameras (there are no guarantees w/3rd party lens, there are some with Canon lenses, but this may be a moot point if the manufacturer provides updates if needed, as Sigma has done with some lenses in the past).
The huge filter size of this particular Siggy isn't a problem for me, since other lenses in my kit use 77mm so I have those with me. It's surprising to see a 50/1.4 require a filter larger than Canon's 50/1.2L, and a whole lot larger than the EF 50/1.4. (Some other Sigma and even Canon lenses use filters I don't have in my kit: 62mm, 67mm, 82mm so I'd have to allow for buying those as well. Just UV and CPOLs mostly... but maybe some portrait filters, plus an adapter to allow ND Grads to be attached. There's some added weight/complexity hauling around additional filters, too.)
The Sigma is a lovely lens, no doubt about it. Well made and good performing. I can see why people choose it. It's always impressive to any seasoned photographer to see a big old chunk of glass like that on the front of a camera! And it comes with a hood, while that's a separate, additional accessory for the Canon. I just hope Canon takes up the challenge and finally comes through with an overdue update of the venerable EF 50/1.4, without ratcheting its price through the roof.