With what little I've seen of Slayers (I've only seen one ep, but in both languages) Hayashibara-sama destroys what's-her-name in the English. However, I don't really like slayers so I wouldn't know any further for that series.
9 times of 10, I watch dubbed anime, because my boyfriend isn't learning Japanese so it's only fair to him to watch it in English. There are good dubs, and there are really, really bad ones:
El Hazard: I believe the creators have said the English dubbed version is the "definitive" Magnificent World OVA. I've got it and watched both languages, and prefer the English by a long shot.
Tenchi Muyo! OVA and Tenchi Muyo! In Love: Okay, maybe I should just say, "anything by Pioneer is good" because for my list it looks that way, although more accurately it would be "everything by Pioneer
that I've seen is good." I absolutely love Tenchi. However, the original OVAs and the first movie are all I've seen of it, and it's equally as good in Japanese. (Achika's big line in the film puts me in tears no matter what language I hear it in.)
***So I don't have page upon page of Pioneer titles, Trigun I've never had a chance to listen to in Japanese yet, but the English is entertaining; Bebop I've only seen one ep of in Japanese and while I don't know about the rest of it, I like the voices.
Maison Ikkoku: Only seen 1-36 in English, and while most of the cast is okay, I hate Kyoko's voice. I've got the entire series on my comp subbed, and I really, really like it so far (especially Akemi's voice in the sub).
Ranma series vs. Ranma movies: Only seen pieces here and there of the series (VHS so English only), and then both movies (first on VHS and second in each language on dvd). Ranma-chan is probably the only role I don't really like Hayashibara-sama in. Other than that, I adore both language tracks for the Nihao My Concubine. In the series, there are okay eps and there are bad ones that I've seen, both for the dubbing and the plot in general. Give me the manga anyday over the anime. (Actually, same goes for Maison Ikkoku: I love the anime, but I cried my way through the third graphic novel.)
Escaflowne: Dubbed sucks. Final word. I like Allen's dub voice, just cause it's Zechs from Gundam Wing, but the rest can rot in hell.
MARTIAN SUCCESSOR NADESICO: Seen half in subbed, all dubbed. Really, really want to see the rest in Japanese, but it's my boyfriend and my (grammar?) favorite anime, so he REALLY insists on seeing it in English, even though he can probably recite the script for the entire series. I do prefer the dub over the part of the sub that I have seen, just because I love Jennifer Earheart's version of Yurika.
Evangelion: Subbed is much better, in spite of Tiffany Grant being one of my more liked VAs.
Devil Hunter Yohko: Only seen subbed, and wouldn't have it any other way.
Also all the voices seem to sound the same, from one anime to the next....
That's because all the VAs have contracts with each studio.
