If VSW stats arent frauds, Yugi is at least equal, but likely superior for Solgaleo vs God cards. I was gonna say general strength might go to Ash, but apparently Dark Magician is also Tier 2, so uhhh I dunno how strong Yugi's lesser monsters are (is Dark Magician even a lesser one?).
Ash is likely faster, tho considering how Ash gives order and Yugi places cards, Id assume realistically Ash cant blitz everything, they both respond to moves in turns basically.
Since Pokemon are "Pocket Monsters", I see no reason to not allow Yugi's card effects to work. Yugi seemingly has way more deadly area effects like denying all attacks, while Ash really lacks them. Heck, if Gengar goes down Ash is supposedly kinda ****** in hax.