Ultron!!Easy Choice..1.) Bleed and Poison Immune2.) Regenerate at 50% & 25% and recover almost 18% health back3.) Degenerate MUTANTS - very easy to kill bishop / wolverine/Kitty4.) Stun at L1 and rotate easily5.) PowerDrain with SP3 - MOST Needed6.) auto-evade (Most used by our AQ in Map 5 against Scorpion SP1 atttack)7.) Evade helps a TON!!8.) Synergies with Hukbuster / kingpin makes him god.9.) He's energey immune (Means, he gets auto-renegeate if he gets energy attacks) - so solid against whoever champs dong energy attacks!!10.) his attacks make BLEED, which helps in many quests. Example: Playng against electro boss, he'll make him bleed to death and regenrate back at 50% health to back to 75%....
I always wonder the Nimrod R4 argument. Where does he benefit you? I have an R3 Nimrod and love him to death - he obliterates mutants. But does so in such a way that my R3 feels like all I'd ever need. What does an R4 get you?