Not sure what this OP has to do with the Sigma 50mm at all??? More of a 35mm vs 35mm topic, or having one very strong 24-70mm vs three decent primes.
Personally, I'd rather use one heavyish lens than deal with changing during a wedding, of all events!
I did sell my 24-70mm v 1 and feel the version 2 is equal to all its hype (eg "like a bag full of primes).
And I love my Sigma 35mm 1.4, as I obviously don't get tired of announcing.
But TOUCHING on 50mm, for many shots, the Canon 50mm 1.4 is great at weddings in low light, with speedy AF, and good sharpness at f/2 - f/8. To me, the Sigma will have to be spectacular to be worth retiring it.
Glad, though, to hear the 35mm 2.0 is so nice.