I have 2 favorite types of companions. First are ones like Compassion, Valarie, Clara, and Donna, who aren’t afraid to argue with the Doctor, and who have writers who aren’t afraid to have the Doctor be in the wrong. I love conflict on the Tardis
Next is more common in teams, like Ace and Hex, Liv and Helen, Fitz and Anji, or Cindy and Gabby. I like when they have a distinct dynamic with each other that’s at least as interesting as the one they each have with the Doctor, and I like when they’re so experienced and have such a complimentary skill set that, as a team, they’re just extremely effective. There’s just something satisfying about a tardis team being together as a unit for so long, and they all know each other so well, that they become a well-oiled machine