Comparing handheld shots done on HP5+ with my Leica M6 to those done with my Pentax 645 with the same film, Pentax wins every time. Comparing my Leica shots to my Mamiya C330 shots with ancient optics, the Mamiya wins every time. I print mostly full frame on 11x14 paper, sometimes cropped. Leica shots easily hold up well at these sizes.
Everybody makes good lenses these days. I know a lot of people consider Leica lenses to be superior to everything else. They are certainly good. But format size matters more. Personally, I don't consider Leica optics the reason to use my Leica cameras. I consider Leica cameras the reason to use Leica cameras.
"All lenses are better than most photogaphers who use them."--Lee Shively