Back in the 1960's there was a very good magazine sold in UK called simply 35mm Magazine. They conducted a test using almost every 50mm lens made by Leitz since
19 somethin. (I can't remember the exact year) they tested the 3.5and 2.8 Elmars, both coated and uncoated. the Summar, Sumitar and Summicron. The camera was a Leica 3G. The tests were made using Ilford Pan F and a developer called Definol made by Johnsons of Hendon, at the time a well known UK manufacturer, Each negative was enlarged 16 times and to be honest there was not a great deal of difference between any of them. Yes the contrast was better with the later lenses and the Summar was a little fuzzy in the corners at full aperture but all versions of the Elmar were simply very good, possibly as good as, or better than the Summicron. the later coated Elmar knocked the socks off the principal current other 50mm lens used at the time - the Zeiss Tessar which was used as a comparison
I believe the current F2.8 Elmar is probably up amongst the best 50mm lens ever made by anybody - ever.
(As a footnote, I was sorry that magazine went out of print because it was simply a no-nonsense, straight forward publication where the reader was not swamped with pages and pages of adverts all more or less pushing the same product, Well written and supported by good photographs).