Originally Posted by pr0xyt0xin
jmc says it very well. And despite his own preference does a great job describing why they are both the best of the best.
Personally I see it like this:
Best villain: Ledger > Hiddleston
Best hero: Downey Jr/Hemsworth/Ruffalo > Bale
Best plot: Joker's chaos > Loki's army
Best battles: Hulk vs Thor, Iron Man vs Thor, Chitauri vs Avengers > ... Batman vs Joker? Scarecrow? Two Face?
Best supporting cast: Alfred, Gordon, Fox, Dent > Pepper, Coulson, Hill, Fury
Best visuals: Avengers by a substantial margin (being 4 years newer)
Best writing: Nolans' epic emotion = Whedon's witty dialogue
Greatest potential: The Dark Knight Rises vs MCU Phase 2 and 3. we'll see who wins.
I know why pure comic fans choose The Avengers. I know why pure film buffs choose The Dark Knight. What I don't know, is which I prefer.
Best Story/Plot: The Dark Knight
Best Hero: Bruce Wayne/Batman
Best Villain: Joker
Best Supporting Cast: The Dark Knight
Best Fights/Battles: The Avengers
Best Visuals: The Avengers
Best Music: The Dark Knight
The Dark Knight wins for me.