This is the first Gym to have two different Gym Leaders between the initial two versions, and the second Gym to have two different Gym Leaders in a generation (the first being Sootopolis Gym between Pokémon Emerald and Pokémon Ruby and Sapphire.)
Iris and Shaga's teams are identical except for their genders; Iris' Pokémon are all female and Shaga's are all male.