While both characters are flawed, I disagree with the majority on here and side with Angier.
He was so friendly and likable at the beginning (which Nolan created purposefully, I know). Then his wife drowns in front of him. Imagine being in his shoes for a minute. That experience would be so traumatizing; it's enough to make anyone go a little crazy.
I'll admit that his obsession with discovering Borden's secret becomes deranged. However, when Angier asks Borden what knot he tied and Borden replies, "I don't know", I was SO infuriated! What a horrible response to give a man who just lost his wife- I don't care that they were twins. I don't think anyone would be satisfied with an answer like that. After that, Angier's character becomes consumed in a competition with his rival and it gets ugly.
Angier puts all his energy in to the competition, but what else is there for him to do? He doesn't have a wife, he doesn't have kids, all he has is "magic" now. He gets selfish, greedy, and a little demented.
I believe his downfall is using Tesla's machine. Tesla asks him if it's worth the cost (the cloning) which was great foreshadowing. Everyone seems to think that him killing his clones is horrible. I think it's a waste of using a clone's potential and also am disgusted with him using the drowning method. But Cutter did tell him "it was like going home", so I don't think he was intentionally trying to hurt the clones, he just cared too much about being the showman for the audience. Also, if he is cloning himself, then isn't he free to do what he wants with his clones?
He thinks he got his true revenge when he shows up as his real Lord self and tells Borden that he framed him and is taking his child away. I don't condone the first part because allowing someone to die for a crime they didn't commit is evil and cowardly. On the other hand, I didn't think it was sad when he took Borden's daughter. First off, she didn't seem sad. Secondly, he was going to take care of her (not harm her), which could have given him a new meaning in his life and she most likely would have been fine. Plus, even is even. Borden took away his love, so he was doing the same. He didn't involve cutter in his framing and I thought that was nice of him. Lastly, he was FINALLY going to destroy the machine and be done with all the madness, but instead he was betrayed by Cutter, who felt betrayed by him, and was killed by Fallon. Angier dying slowly was very sad to watch- atleast Borden's death looked quick.
I do feel bad for Fallon. He was clearly the better half of the duo and he deserved to be reunited with his daughter. At the same time, I think he is the biggest coward! He didn't HAVE to go along with Borden's plan, he could have CHOSEN to tell Sarah the truth, but instead his dishonesty caused her to commit suicide. (Rebecca's acting was superb btw!) Borden and Angier were stupid for letting their competition go so far, but Fallon chose to be Borden's sidekick instead of his own person, which is far from admirable.
Anyway, sorry for this crazy long post! Insomnia is the worst. I definitely understand and respect that others have different opinions than me. To sum up, maybe I liked Angier more because I felt sorry for him and understood how he could turn out the way he did. I also just found his character more interesting, but Borden/Fallon was great too and Christian Bale was phenomenal! So was Hugh Jackman. Nolan picked top notch actors to play the two characters.