Arc day is singularly better than any single day card Ascot can hope for. On the other hand the Royal Meeting as whole probably shades Arc weekend as an event.
I'm not so sure that's as true as you might think, and I'm sure that's what the BHA were taking aim when they moved Future Champions Day onto the Champions Day window. Splitting courses however, was never likely to work (worth trying, but unlikely to capture the imagination). Newmarket isn't geared up to host a big international meeting. It lacks infrastructure and charisma
The French certainly have the edge in the 12F department because of the Arc, but going forward, is 10F's not going to be come the new 'blue riband' distance? It's the trip that the American breeding industry are increasingly interested in, and you only need to look on a graph at field sizes between the Derby and Prix Jockey Club to realise something is happening. About a decade ago Derby fields were much bigger than they were at Chantilly. Not any more. If you take out Aiden O'Brien (who has single hadnedly been keeping the Derby going) the threat to the 12F trip becomes even more apparent. Perhaps they ought to rename the Champion Stakes, the European Champion Stakes
Most races have to start off on a lower grade of course, but there's no reason to think that the Champion Sprint Stakes won't become a Gp1 race imminently. The Prix L'Abbaye is Gp1 in name only, and I reckon the Ascot race is stronger and has greater potential 6F's, which more of the international sprint distance.
The fillies and mares race (nice American title) has already been upgraded to Gp1, and at 12F's is a bit of an alternative to the Prix L'Opera and also allows fillies who ran in the Arc a chance to notch another Gp1 quickly if they're up to it. I'm not so sure that it isn't stronger than the L'Opera already
The Long Distance race and the Prix Cadaran are just supporting acts anyway
Ascot has the edge in the only other slot left. The Prix Foret at 7F is unique, but in terms of being an end of season Championship decider it falls short. The mile division by contrast is represented by the Queen Elizabeth
The primary races left therefore are the 2yo races, and again I think the BHA are sensing that they hold the edge here if they were able to prise them away from Newmarket. The Dewhurst, Middle Park, and Rockfel are a stronger trinity than the Bousacc and Lagadere. This is where the French hold the edge, that and the fact they have a second day with four Gp2 races. If Ascot were able to take over the Newmarket Future Champions day card(s), they would have the better racing package, with the stronger brand name, and be in position to place themselves on the apex of the European scene. The only thing the French could fight back with is prize money and a single race