I've had about every 50 made for Leica and Canon RF cameras along with Nikon, except for the Zeiss. The 50 Summicron, current glass is the one I always come back to. I have both a tabbed with current glass and current model with built in hood and can see no difference. I'm led to beleive that coatings have improved the current model, but again, I can't tell one way or the other. The Summicron is about the sharpest lens I have used without being hard or should I say harsh. Also the color rendition is supurb. It makes me a better photographer, or at least I prefer the rendition of the images with the lens more, if that makes any sense
To Compare, the 35 Summicron Asph get's a little harsh or maybe cold at times where the 50 does not.
The Summicron is best 50 I have ever used, but either one is an excellent choice. Keep looking at images shot with both and you should be able to get a feeling of which will be the one for you.
Randy