To me mean/antagonistic rivals aren't necessairely better but I feel they fit my criteria that rivals need to have to be good rivals, easier then friendly rivals. First a rival needs to be challenging. A rival that isn't challenging, is't a good rival. This means that with the lowering of the difficulty of the games and the improvement of player skills in pokemon over time, didn't do the friendly rivals justice which were introduced in the later generations.
Second a rival battle has to mean something, there needs to be a stake/reason to win. Mean/antagonistic rivals meet this criteria , because they either have an opposing ideology and/or are just play mean and insult you. Proving them wrong is the reason to win. Fern, blue and red easely fill this but with the friendly rivals this is most of the time lacking. That being said overcomming a chalenging opponent can be a good reason to fight but pkmn tends to not go that route. Wally and Hau are the worst offenders to this principle.
Third a good rival, makes you want to interact with him. Here is where friendly rivals easily fall flat on their face, most of the time they are boring. This is also why I think barry wasn't a good rival for me, I didn't like his attitude and behavior. Every meeting with was a test of my patience and I basically groaned when he came on my screen because to me he acted like a hyperactive monkey. That being said the interaction between character doesn't need to be positive: loving to hate is perfectly valid and mean rivals also fit this criteria easily . As long as the rival interactions (with the player) are good it helps being a good rival.
So yeah I will not say friendly rivals are bad (Cain is for instance a good rival) but they rarely fit my criteria for a good rivalry.