Ah, but how easy is it to improve their power rating?
Polar Star costs 10 to level up once, 20 to level up again and 10 to max.
Bubbler costs 10 to level up, 20 to level up again and 5 to max.
Nemesis needs 1 damage to level down.
Okay, so the Bubbler = Polar Star when it comes to leveling...