There are several things that sets Leica cameras ahead of Nikon:
manual film rewinding
sound from inside the cameras and feel while rewinding
sound of hit of rewinding laver on way back
sound of the shutter movement
ability to use Leica lenses
confidence it gives to user
Are they really ahead???????
I think that somehow Nikon F6 (or even F2as) coupled with F1.4/85 AF Nikkor, or some more good lenses form Nikon or Zeiss is nothing behind.
many say LeicaflexII is still the choice No.1. I think personally that R6.2 is better choice (it is also no battery camera). Leica R8 is actually my first choice when consider all Leica qualities from above, in spite it is dead without battery (last 2-3 years).
Again, the biggest R Leica quality is that it uses Leica lenses. Today (in Euro-) lens manufacturers cannot use lead any more. It also sets ???? on new Leica lenses and also why Zeiss make lenses for Nikon in Japan. Leica make a try to design new lenses as aspherical (as replacement for lead) but I never could see "photo-good" aspherical lens. Also today Leica set of lens-designers (worst ever in Leica history) are far behind Nikon's engineers which also got good design history from behind. So Leica quality today is REALLY big question. Shortly, I would say Leica today do not worth even and fraction of the price you will pay for a new stuff.
If you still like them go with old lenses but take care not every Leica lens will fit every Leica camera.
www.Leica-R.com