That's nice to know. Not certain how this canon lens would differ from or show advantage to my 90mm tele elmarit 2.8. The 135 is clearly a winner. I like the ability to mingle reasonably close in the crowd, but take pictures without intruding to closely. Leicas may be quiet (not really to current standards of silent shutters) and sort of small, but they are not incognito by a longshot.
One stop....is one stop. In the era of faster films, this is less of an issue. Cinestill 800T can be shot up to 2x without really getting into pushing. Although I understand it can be pushed substantially. One stop can be helpful if shooting Velvia 50 or something like that. I also like using Fuji Natura, but almost exclusively on my Natura S P and S.