Interesting. Thanks for the info.Yeah, as Kit said, almost certainly. The old one is a traditional double-Gauss with fairly poor performance wide open. The RF seems to be a modern "pickle jar" with a considerably more complex optical design. The weight of the latter is 950g compared to the former's 580g.
Yes, I've been somewhat underwhelmed with the 50 1.2 (EF) IQ-wise, but it has still gotten me a few unique perspectives. Hopefully this signifies an update of the EF version in the near future.