I think Alder says in Black 2 that the gym leader is supposed to play to their opponent's level in order to give them a close match which will better them as a trainer. So if a kid from Opelucid City started out on a journey, Drayden would probably fight him with just like a Axew and a low level Druddigon or something. But by the time he got to Virbank and was stronger, Roxie might be using Drapion, Toxicroak, Nidoking, etc. --- Terry McAuliffe for Governor '14
I've always subscribed to the different Pokemon depending on badges idea but I try not to think about it too much either way because it makes the Gym Leaders look bad still and is kinda disillusioning.
It's been confirmed that Gym Leaders use different teams depending on how many badges their challenger has.
If you skip Jasmine and Chuck and go right for Pryce why would he use his team for when a trainer has 6 bages when you only have 4?
That's more of a game design issue than anything. Gotta remember that gameplay/story segregation. --- I would prefer to be known as BlackWaltzTheThird, or just Waltz for short. Official Froakie of the Pokemon X boards.