First off I'm going to say that I prefer Subs, but I really don't care if a person likes Dubs or not. I really only care if you watch both versions (or at least one completely through, and the other watch a couple of episodes to compare) before you say you like one over the other. I'm actually studying Japanese (I don't know too much though) so when I watch Subs, I can understand a little of what's being said. To me at least, the quality of the voice actor is VERY importaint, but not as importaint as another factor, Location.
What I mean by this is that where an Anime takes place mainly decides in what language I watch a series. In series like Baccano, Hellsing, Cowboy Bebob, or Black Lagoon, where only 1 or none of the main characters is Japanese, and it doesn't take place in Japan (or only for a short time) I much rather watch it in English. I mean, perfect Japanese coming out of an old English Gentleman's mouth!? That's really akward to listen to for me. (Black Lagoon has a special honor in this case. The Creator himself, Rei Hiroe, said that all the dialogue in the Manga and Anime is supposed to be in English unless otherwise stated or shown in the story. Japanese is only done for the audience. There you have it! Right out of the horse's mouth! I mean, when you think about it, with such a multi-racial cast, the only common language the have amongst them is English! The same logic works for Cowboy Bebob). Not to mention these shows have absolutely brilliant Dubs, with excellent VA's.
On the other side of the coin, when you have a mostly Japanese cast or a Japanese setting (which is A LOT of Anime, or at least the ones I watch. To me, even imaginary worlds with characters that have just happen to have Japanese names or slightly modified Japanese names count in this catagory, ...... somewhat) I prefer to watch it Subbed. To me, to hear perfect English coming out of a Japanese High Schooler's mouth is odd and akward to listen to. Not to mention something like Lucky Star, where they keep in Japanese words that are not honorifics are kept in, like Onee-chan, or the random meaningless noises, like pittochina and the like. That's really creepy and odd to me. When it comes to what you should and shouldn't translate, I believe the ONLY thing you should never translate is "Cultural Terms" (by this I mean names of food, places, weapons, martial arts and martial arts terminology, etc. Chinese Marial arts and their terminology should be changed into the apropriate Chinese however. Usually Mandarin). For Honorifics, it depends. (if the setting and characters are heavily Japanese, keep them in. If the setting and characters are heavily Western or International, give English aproximations or just drop them all together). However, terms like Onee-chan or Baka, which have very clear translations that are not tied up to any one culture SHOULD be translated. The fact that I prefer Sub in these situations is very much true, even if the Dub is good!
To give examples: Haruhi Suzumiya and the 1st Negima series. I thought both of these dubs were really good. (Even though I thought Aya Hirano's Haruhi sounded much more youthful and vibrant that Wendee Lee's Haruhi, but I think that has more to do with the fact that Aya Hirano is now 22, and Wendee Lee is now 54. Aya Hirano sounds more youthful than Wendee Lee because she is MUCH younger than Wendee Lee, and no amount of acting is going to change that. And the Negima dubs are excellent in my opinion, even Negi's voice. I didn't think it was annoying or grating, and you have to commend Greg Ayres for being the only male VA, at least to my knowledge, to voice a young pre-pubesent boy. This role is usually voiced by older women. Negi's Seiyu is in fact a woman. But while the voice acting was great, it still couldn't save the 1st Negima series from being horrible in every possible way. I don't mention the 2nd series, which I actually liked, because it's Dub was bad. Not because of voice acting, which was very well done, possibly even better than the 1st series, but it's Humor and Referances were LOCALIZED and AMERICANIZED. That is utter bullshit, it is the purest of pure evil when it comes to Dubbing Anime. I don't care WHAT the reason is, you NEVER, EVER LOCALIZE a Dub). However, as the examples given above, when I watch these series, I still watch them Subbed. I still personally find the fact that unaccented, perfect English is coming out of their mouths to be strange, at least to me. (Not in the case of Negi, however). However, if the setting and characters are heavily Japanese and the Dub is good, I'll switch back and forth depending on my fancy that day (I still go to Sub more often). But if a series is heavily Japanese and the Dub is bad (like Azumanga Daioh and Lucky Star, for reasons mainly of voice acting) I never watch the Dub again. (There is only ONE exception to the rule: Samurai Champloo. It may be heavily Japanese, but the Dub is SO DAMN GOOD I don't like hearing it in Japanese. In my mind, it is the best Dub ever made).
But Dub or Sub, you should buy the DVDs if you really like or love a series. Not all of us have multi-region DVD players, so not all of us can get the Japanese DVD release shipped to us the minute it comes out. So most of us in the Western World have to wait for the region 1 (Dubbed) DVDs to come out. If you don't buy them, the companies tank (like Geneon) and we get no region 1 DVDs at all, and our source of Anime dries up. But hey, if you don't like watching Dubs (like me for the most part) do what I do: go to the disc options, and SET THE LANGUAGE TO JAPANESE!!!!!
I may prefer Subs, but if you like Dubs, that's no water off my back, as long as you experiance both Language options to judge which is better. The only thing I hate is when people say they hate Dubs and they use that as an excuse so they don't have to buy the DVD. The reason why Geneon went bankrupt and the reason why Gonzo is in spiraling debt is because of people like you. If you don't support the industry that makes your hobby, you can kiss your hobby goodbye.