You posted a question and Bernard answered it, OK?
DxO tests most third party lenses on both Nikon and Canon. Their ranking is based sharpness. As the Nikon has a higher resolution it will normally have a higher rating. If you take the time to learn to use DxO-mark you can compare lenses and find out about their strengths and weaknesses.
It is a bit unfortunate for Canon that Nikon has better sensors, in most respects. Canon's sensors are great at high ISO, that is much depending on the technology used. On the other hand I would say that mostly, both systems are good enough. My best friend has a Canon 5DIII and I have Sony Alpha 99 and also a 39 MP digital back. I don't think my equipment makes better pictures than my friends camera. Even if the Alpha 99 has better DR and the digital back quite a lot more pixels.
But, I would also not buy an Otus, unless I wanted to shoot at f/1.4. I would also expect that Sigma will come out with a 50/1.4 Art lens that almost as good at one fifth the price.
As noted before, quantitative is interesting but not like tasting the pudding. Thanks for answering. Makes my other post moot.
Poor benighted Canon users... no 50Mpxl to brag about... yet, I suppose.
Guess my images, and those of other Canon users are not as good as we thought.
In any case, after a life of working with very sophisticated equipment I can say that Quants have their way of looking at things and tend to be very rigid. Personally I think both Quant and Qual are important lins to follow...but that's just me.
As always, thanks...