Who would give you the higher chance to win a title in the next two years? You as the manager already have a team which is solid in defense and solid in offensive, but it lacks a star player to make it a serious contender. You can either add Embiid or Doncic to that team.
If I already had a ball dominant guard and a second decent combo guard I’d pick Embiid. Luka is a egregious liability on defense and if his offensive usage is down, it probably limits his effectiveness.