In this gen characters' ace are those who can gigantamax and some work pretty well, others are pretty off and forced like Melony-Lapras, Bea-Machamp, Allister-Gengar.
But you can say "yeah who cares those are gym leaders", but then we see Hop. Hop is our rival and people even says he has the best character development (while it's really not), but then we see him in the end having a Gigantamax Corviknight, he will use it in the rematches. A corviknight, a pokémon he never spoke about during all the journey, instead of his dubwool. Even Bede had a backstory about his Ace, but why Hop not?

i know even Marnie's one is strange, because of her morpeko, but Grimmsnarl works as a counterpart of Hattereene at least.