Is Schneider 80mm lower optical quality than Leica R50?

My bet would be the 120 Schneider. Use the mirror lockup with your Rollei.

Thank you, D Purdy ^_^
Does it mean 120 Schneider lens naturally better than Leica R in optics
or larger film size advantage printed in 4R or 8R?

At least to me, Leica and Schneider lenses seem to be at nearly opposite ends of the spectrum in what they optimize for. Leicas have low macrocontrast but high microcontrast. Schneiders tend toward higher macrocontrast and lower microcontrast.

Leicas also tend to have a fairly smooth roll-off in quality as you get to the edges of the picture. At least the 80mm Schneiders I've used had almost perfect quality out to roughly the center of the edge, but then dropped off quite sharply from there to the corner.

The difference in format also means the Schneider/Roellei will require that you stop down further to get (roughly) the same depth of field. If you need/want a lot of DoF at low light levels, that will tend to favor the Leica. If you want minimal DoF at higher light levels, that will tend to favor the Schneider/Rollei.

The pictures you get will have distinctly different characters. Without knowing more about the picture(s) to be taken, however, it's essentially impossible to say which will really be "better".

It would be very difficult to match the tonal and sharpness qualities of a good lens and 120 size film with any 35mm lens and film. Schneider lenses are top quality and especially the 80mm Xenotar. European design lenses have a very natural feel to them.

If you put a Leica lens on a 120 camera, you would get a circular image with dark edges. How would that be better?

Thanks Jerry Coffin a lot for the detailed reply!
i.e. for the print size over 8R, to use 6008i + Schneider is better with higher macrocontrast.
DoF difference, thanks!
Landscape photos usually for me.

Thank you, D Purdy!
Yes, maybe very little difference in 4R for these 2 systems.
I like natural feel, so I prefer Leica,Schneider lens, Zeiss not my cup of tea.

Thanks Edward Ingold!
You said right, perhaps someone has ever tried 120 lens into 135 body.

The 120 format will walk all over ANY 35mm film camera and lens. The lens has very little to do with it - 35mm film is simply too small and grainy to capture high quality images.

Thanks Rodeo Joe ^_^
I also like 4X5 format, but always tripod, oh...
120,135 are more portable

Not apple to apples. Different lenses, different formats. THe question is about lens quality, but they will never be seen against each other. Both are fine lenses, but I really like the Schneiders on the Rollei, and have a bunch of them. The Leica R lenses are fine too, but haven't done a head to head on them. R lenses on the DMR were nice - it would be have been good for Leica to find a current home for all of those good lenses out there....