I was not referring specifically to Canon and Nikon (I used them as an example of sensors with very different resolutions), but in any case, it seems here as well nobody seems to have, or know about, any data whatsoever available to support my friend's claim (which in short is just: still today resolution itself is a dominant factor in determining noise and therefore img quality, to the point that one who does not need a very large image, will be best with a lower resolution sensor).

Interesting.