From a Porsche perspective:
my Boxster needs N rated tyres (produced by Michelin, Pirelli etc). At the front, 235/35 19, the load index of an N rated tyre is 87Y. All non N rated tyres of the same size are at 91Y.
At the rear, it's 265/35 19. N rated load index is 94Y. All non N rated tyres are at 98Y.
Certainly in Porsche land, N rating does make a difference.
my Boxster needs N rated tyres (produced by Michelin, Pirelli etc). At the front, 235/35 19, the load index of an N rated tyre is 87Y. All non N rated tyres of the same size are at 91Y.
At the rear, it's 265/35 19. N rated load index is 94Y. All non N rated tyres are at 98Y.
Certainly in Porsche land, N rating does make a difference.