Many trainers in Pokémon NEO X & Y now have a greater amount of Pokémon with custom movesets, higher IVs and items.
Gym leaders have been significantly upgraded. They get progressively tougher in terms of amount of Pokémon, IVs, access to Mega-Evolution, move-sets and items!
There are also a greater number of rotation, double and triple battles throughout Pokémon NEO X & Y, so be prepared!