"Pokémon SS or Pokémon BD"

Hi! So, basically what the title says. I’m debating whether to get Sword and Shield or Pokémon Brilliant Diamond once it releases while we wait for Gen 9. What are y’all’s opinions? FYI, I haven’t played the original Pokémon Diamond (I prefer Dialga over Palkia c:<). The reason why I’m debating this is because Gen 9 is coming soon which means SS will start losing players so I’m not sure whether I should get SS or BD. (Sword and Shield & Brilliant Diamond) via /r/pokemon https://www.reddit.com/r/pokemon/comments/qtuak3/pok%C3%A9mon_ss_or_pok%C3%A9mon_bd/?utm_source=ifttt