In the end, I bought 2 cables for myself and a colleague. The two cables were appearing in the "snow" on the screen and the quality was slightly better if we made an effort of abstraction of the noisy image.
So back and Amazon has proven its reliability in paying me very quickly!
Now I bought the official Nintendo cable and I have no worries. I confirm that the image is improved, but with some games, aliasing of the display is surprising (DBZ kind for which it seems to have cut paper figurines :-)).