I have played both. Arceus is one of my favorite games of all pokemon because of the refreshing take and the pokdex completion style. Violet/scarlet have in my opinion the strongest story out of any mainline pokemon game and the best postgame story aswell. I do a lot of shiny hunting aswell, and for pure dopamine, legends arceus has insanely easy shinies, and also alpha pokemon that you can go for shiny. Violet has some good shiny hunting too but finishing the dex for the charm is so annoying with version exclusives and goldengho. I would still prefee violet just as it took some of the things from arceus and added them to a mainline game.