For what it's worth, there is a test on the internet (i think on MFlenses) where the 50/1.4 SSC is compared to many other 50/1.8 and 50/1.4 lenses, including Pentax, Minolta, Nikon and others; and it has visibly higher resolution.
Again, this result, as well as the opposite result, is influenced by sample variation and condition of the lenses. Also bad repairs. I have seen technicians here dissasemble and reassemble a lens without marking down the alignment of each one, etc.
On a french early 90s test on a website, the Canon FD 55/1.2 NON-aspheric is tested against many lenses including a Nikon 50mm rangefinder and a Leica 50mm rangefinder lens; the FD had significantly, drastically higher contrast and saturation than all of them, giving a hard, "crisp" look. (The Nikon and Leica offered higher resolution and much lower contrast, a much lower softer look). Those three (C, N, L) were higher performing than the other lenses tested, which I think included Minolta and Pentax.
Magazine tests of the era, which I have somewhere on my hard disk, show that the Canon 50/1.4 is slightly, just very slightly, better performing than the conteporary Nikon, and those two being better performing than the Minolta, Pentax, and Olympus offerings.
In fact in the early 70s Canon was advertising on magazines the result of a massive lens test conducted by a japanese university, where Canon lenses came out on top (1st place) on many of the categories (i.e. "100mm lens" category, etc).
This is not any chance; by about 1968 it was evident that Canon had made a massive inve$$tment on its camera lens division, and dedicated a big budget for R&D. A full array of higher-performance FL lenses was released that year, no doubt the designs being created in advance for the release of the Canon F-1. The goal was simple: For the F-1 to have success, it's lenses would have to outperform the Nikon offerings!!