FMA Brotherhood is practically the manga word for word, panel for panel. xd
Overall, Brotherhood is much better than the FMA anime. The animation is several times better, the voice acting is second-to-none, the drama and suspense is very gripping, and the story is far more involved and innovative. Broterhood really brings the manga to life and gives the characters a whole new level of depth.
For example, Hohenheim of Light in the FMA anime series played a rather minor role, was depicted rather harshly, and was a very flat character in literary terms. Van Hohenheim, however, possesses much greater character depth and focus on his past. In general, he's truly a sad character, and Brotherhood has a way of making you feel sorry for him because of all of the grief he is stricken with (i.e. being unable to be with his children, not being able to protect his wife, having all of his friends and his entire country die before him and ending up with over half-a-million souls in his fake body).
The Homunculus in Brotherhood had much more depth to them as well. Each Homunculus ended up being pretty epic in their own way, but at the same time, they had their own shortcomings that they hid despite their pride in being Homunculus and supposedly superior to humans in every way. With Envy, I absolutely hated him in the first series, but in Brotherhood, he was funny, sadistic, and manipulative character whom one would have disliked strongly because of the way he treated every other character (and because he killed Hughes). However, Brotherhood somehow manages to make you feel sorry for Envy as he dies after Mustang completely incinerates him over and over again.
And, I think we can all agree that Brotherhood Mustang is a thousand times more badass than Mustang from the first anime.