As to the original question, I use Leica rangefinders and Canon EOS SLRs so I use both manual and autofocus lenses on 35mm cameras.
The rangefinders manually focus very precisely under most light conditions but I have satisfied myself that, under low light conditions with SLRs, I am not able to manually focus wide to normal lenses as accurately as using autofocus. This is comparing manual focus Nikons to autofocus Canons--the photos with the Canons will consistently be better focused. Long lenses are a little different for me. If the light is really low in contrast, I'm better off manually focusing anything 300mm or longer. If the light is bright and the contrast is good, autofocus is more accurate and faster. That's just the way my eyes work these days.
I prefer using prime lenses to zooms and the Canon prime lenses I own have very good manual focus rings and their optics are better than I need for the photos I do. The Canon consumer zooms have manual focus rings as an afterthought but they operate adequately and their optics are pretty good. I have two Canon L-series lenses--70-200/2.8 and 400/5.6--and the manual focus rings and optical quality are excellent.
Plastic in the lens barrels make Canon non-L prime lenses and consumer zooms feel less substantial but I can't say they're inferior. I recollect that when I used Nikon manual focus equipment, I wore out several manual focus Nikkors with daily professional use and abuse. I don't expect any of my current equipment will ever be subject to that heavy use again.