Well I was actually impressed with the Full Metal Alchemist dub, though I didn't see the original Japanese sub, the english dub was really good.
But Naruto is different, there are a lot of things I would bet the Dubbing company would **** with. A lot of techniques names will be changed, into something more English friendly, but usually much more retarded too. I have a feeling they would be changing the names of things like Rasengan, or Chidori, because they're not in the English language. If you look at DBZ, Kamehameha is actually in the english dictionary, Makenkosopo (sp) was not so the name was changed to 'Special Beam Cannon.' There's no way they'll go with names like Chouji, Sasuke, Shikamaru. Even Hokage was changed, from what I saw in the english trailer. Changing names after I've already seen a good chunk of the Japanese version will not get a good reaction from me, or anyone who's seen the Japanese version.
I mean just imagine Naruto performing 'Master Chakra Wave,' or some other move that was named equally retarded, since dubbing companies are absolutly terrible at choosing replacement names.
Small changes like that can easily ruin a series. I'd go with Japanese on Naruto.