I like the dual dynamic between Steven and Wallace, pretty unique as far as champions go. I feel that's more accentuated during the times Wallace is the champion (Pokemon Emerald, the Adventures manga, there's probably a few others). I also like Wallace more as a character from the original games. It feels like he represents the region better than Steven as well, being a water type trainer who also focuses on beauty and contests, for the ocean region that introduced Pokemon Contests, so I find it more fitting for him to be the champion and ultimate challenge of Hoenn.
I do think they should have given him more variety in his team when making him a champion though. And at the same time, I have a soft spot for Steven ever since the ORAS demo where you went on adventures with him and had a bunch of small character moments. He was also given more moments like that in the remake proper. He also, in a different way from Wallace, represents Hoenn pretty well, kinda like how Maxie and Archie represent land and sea and are supposed to have that contrast, something similar happens between the champions I feel. It almost feels like they were meant to be version-exclusive champions originally but ended up scrapping the idea. Who knows. Ultimately I think I like Wallace more as the champion carrying the mantle (literally, with his cape), and Steven more as a wandering Red-type trainer who used to be champion.