16 was always a "good android", since he's more of a "pacifist" type of guy that doesn't want to fight, because it could also destroys the environments.
Meanwhile, 17 & 18 acts like a couple of "shitty brats" that still on their puberty with their unstable emotions. So they could still be changed with the right guidance, which was happened during the series.
Unlike the 3 Androids, Cell is embodied with Dr. Gero's ambitions, which is to rule the world. So it's very unlikely that he would switch sides, since he's evil to the core. Even Goku didn't want to consider him for the Tournament of Power, since he knows that Cell can't be reasoned with.