There is no question that selected Nikkor lenses are of highest standards, similar to Canon...etc.
Zeiss glass for selected lenses has also very high standards.
Leica glass for M or R has as well highest standards of light manipulation.
So what is the difference if there is a any difference?
In my mind, there is a difference although subtle in certain cases, but the difference is there for the one "who wants to see" and "who can see".
A difference does not necessarily mean "better" technically or subjectively although both can be part of the equation.
Let's take a common focal lens of say 80mm (which happens to be my prefered focal).
The contenders are:
- Nikkor 85/1.4 D - G
- Nikkor 85/1.8 G
- Canon 85/1.2 L
- Zeiss ZF2 85/1.4
- Contax 85/1.2 Anni 60
- CZJ Biotar 75/1.5
- Leica R 80/1.4
- Leica R 90AA
I do not intend to do a shoot out as my mind is already made up and boils down to 3 lenses:
- Nikkor 85/1.8 G for day to day demolition derby
- Leica R 80/1.4 for classical and romantic beauty
- Leica R 90AA for perfection redefined
The other lenses sleep in the cabinet.
Morality of the story: There is no point dliberating on the value of highest standard of lenses in the same focal lenght as they will all translate light to satisfaction. What is left is the finicky extra quality that you get with a trained eye.
Does it make a difference? Hell No! unless you are a pain in the A$$ like your's truly....But then again, I am a mere wanton photographer with a feeble mind and deep pockets!