I first experienced the Japanese voice track when Brotherhood was being streamed by Funimation back in 2009. Although I found it distracting to have to keep reading the subtitles while watching the action, it did give me an appreciation for their efforts. In spite of that, I really really like the dub-- largely because of Vic Mignogna as Ed, although Travis Willingham as Mustang and Sonny Strait as Hughes are also a HUGE entertainment factor. I do think both versions of Fullmetal generally have really good dubbing on them, but what does everybody (anybody) else think?
i haven't gotten around to watching the subbed version of either anime yet, but i do intend to somepoint in the near future. i've seen the dubs though and from what i've come to understand they keep the translations and such very close to how it was in the original audio, and the voice actors still do well getting emotions and tones of their voices to match up to the characters very well. so i'm not sure about subbed yet but i do like the dubbed versions
For most of the anime that I watch I prefer the dub so that I don't miss any of the action but there are some anime that I prefer the sub version better. For example I like Yu-Gi-Oh! 5D's in dub, on Saturday mornings I would watch it in English so I am use to hearing it in English; I am normally up late on Saturday nights and on Adult Swim they air Bleach, Fullmetal Alchemist:Brotherhood, and Kekkaishi (I think that I spelled that correctly), also Fruits Basket. I like Vampire knight and Vampire knight: guilty with subs, Fullmetal Alchemist, Soul Eater, Naruto and Naruto Shippuden (I believe that I spelled this one correctly). Even though sometimes I prefer to watch Naruto and Naruto Shippuden dubbed so that I can take in most of what is going on and not worry about what the characters are saying or talking about. I still like both versions though but, it really depends on which anime that I am watching.
I've only seen part of the dub, but I love it. It's a bit weird adjusting to different voices at first, but for fma, I think most of the English voices fit well with the characters.
Now if we were also talking about the Hetalia dub...FUNIMATION FTW.