Its ridiculous to compare Grand Prix and Le Mans
Grand Prix (IMO) is a better movie, as in i think it appeals to a wider audiance with its storyline and melodrama
Le Mans should be viewed almost as a documentary, and not as a "movie" in regular way. There is no better footage of classic motor racing than whats in Le Mans. McQueen definately got it right for car nuts.
Once i figured out, it made my most recent viewing way more enjoyable. Really was blown away.