Bittersweet, with the richness of Grand Marnier balancing the bitter liqueur and lemon juice. (I'm guilty of rebalancing this cocktail and adding the prosecco.)
I used a South African sparkling wine, since that was what I had to hand. Actually worked very well, though I added a splash more of that wine, since the wash line was lacking. Still tasted good. Nice Cognac-orange liqueur to balance the bitter finish of the Campari in it.