Wally is more effective specifically for me because he reminds me of myself. I also like shy characters.
Hop I can empathize with because of the inferiority complex and feeling the need to arbitrarily "prove himself" to others because he's constantly comparing himself to others and doubting his sense of utility and accomplishments. I totally get why people like him and I've warmed up to him now, but Wally was Gen 3 and so it was the first rival to ever hit close to home and boy did he hit hard.
Honestly, I feel like Galar's rivals would've generally been more widely appreciated if Hop just eased up on the encounters a little to allow room for Bede and Marnie to get more time.
Oh, and if we're counting anime, Gou from what little I've seen is shaping up to be a fav of mine. But tbf I like a lot of Ash's friends like Brock, Misty, Dawn, May, the entirety of X and Y's cast, and now Gou.