Here are both Giratina battle themes from Platinum and BDSP played at the same time. Both tracks were aligned using Audacity. I thought they sounded great together, so I extended them. Enjoy! :)

Battle! Giratina Pokémon Platinum Composed by Junichi Masuda and arranged by Go Ichinose
Battle! Giratina Pokémon Brilliant Diamond Shining Pearl Composed by Junichi Masuda and Go Ichinose and arranged by Shota Kageyama