What I've found I like about rangefinders is fairly simple.
1) I can't easily and reliably focus on ground glass. Even with MF or LF cameras on GG I spend LOTS of time with a loupe to get it right. Even then, I just don't see the image like others, and I get more out-of-focus shots than I'd like.
Advantage for me, RANGEFINDER.
2) Every manufacturer seems to have both WONDERFUL and HORRIBLE lenses. I'd have to carry a camera around for each WONDERFUL lens. Canon's 50mm f/1? Nice lens. I'd have a camera for it. The 1.4 is only average, though. Same with the Nikon. For a good 50mm f/1.4 I'd need an Olympus or Konica. 85? There are several to choose from, of course, some better than others. Wides? Who makes a better wide than Zeiss?
Or I could just buy Leica and have all I wanted in the kit- of the lenses I personally generally consider "above the crowd" in every focal length I'd like to use. The same could be said of my (now gone) G2. I don't have to guess who has the best 50- it's the one that fits my camera and known for being "great!" Best 90? No contest for me. Best 135? Well, several fill that range, but the Elmarit is pretty good, even for an older design. It has goggles. How cute is that?
The 21mm isn't as well known, but if Zeiss tests as well as the G2's did, I'll probably buy one.
My point is that rangefinder lenses aren't necessarily better, but modern rangefinder optics are more consistently so. In other words, the average seems higher. I like that. There are few dogs, even for CV lenses- and trust me, there are PLENTY of dogs in SLR lenses. CHEAP zoom anyone? A few are "decent," none are bright, and they are complicated-er by the fact that one can simply stand still and frame... One doesn't have to walk around and learn or predict their subject, something that would be very hard for me to do.
🙂
ANYWAY.
My favorite lenses are all rangefinder lenses. All the lenses I own (well, the 127 and 150 are average) for my Mamiya Universal are good. My Leica has good lenses. My Kievs... SOME of them are simply outstanding (J-9, on the Contax!), some are good (CZJ Sonnar f/1.5 50mm).
But then, I don't complain about my SLR's lenses- I gave up on them, so don't have to worry.
Oh, that's not completely true. My Mamiya RB gives wonderful pictures, and is still an SLR...
ANYWAY.
Rangefinder = necessarilly better? No. Seems to be a higher average, though.