It depends on what content you're looking to use them for. Corvus handles short to mid-length fights better than most champs in the game. Medusa is one of the best counters to robots. Hyperion is straightforward with tons of damage, but is more RNG dependent, which some people really don't like. What is your next goal in the game once you take one of these to R5? Do you have any notable gaps in your roster? For instance, both Medusa and Hyperion are immune to Poison, while Corvus can handle Bleed and Coldsnap.
It depends on what content you're looking to use them for. Corvus handles short to mid-length fights better than most champs in the game. Medusa is one of the best counters to robots. Hyperion is straightforward with tons of damage, but is more RNG dependent, which some people really don't like. What is your next goal in the game once you take one of these to R5? Do you have any notable gaps in your roster? For instance, both Medusa and Hyperion are immune to Poison, while Corvus can handle Bleed and Coldsnap. magneto is the best robot counter no one comes close
Hyperion is simply better than corvus. Notice there is no 6* hyperion, that's on purpose.