It would be noticeable if all content authors were experienced in the medium, but in the transitional period there would be little obvious difference, because t

It would be noticeable if all content authors were experienced in the medium, but in the transitional period there would be little obvious difference, because the entire culture of digital imaging, including almost all existing content, is based around the limitations of RGB displays and images. If you want a somewhat relevant test, you can try comparing images produced by a photo printer with images printed in old newspapers. Having a larger gamut makes the former much more vibrant. Current displays produce very intense orangish-red, purplish-blue, yellowish-green, and reddish-purple colors. So the differences with a hypothetical >5-primary display are going to be most noticeable in the blue-green range, and oranges and yellows.