I think Katie was the best of the league-only rivals. Of the Hoenn league battles Ash's battle against her stands out to me better than either Morrison or Tyson. All others were just put in as a ploy for Ash to lose against.
For anyone interested, by friend code is 5257-9947-2315. If anyone wants to add me, remember to PM me so I can add you too.
My friend safari contains the ground type pokemon Phanpy, Marowak and Palpitoad.
Current Y team consists of Delphox, Pidgeot, Raichu, Simipour, Charizard and Gogoat.
In training: Wartortle, Bulbasaur, Chespin, Froakie, Combusken, Pangoro.