I'm always on the side of: it's a personal choice, however you most enjoy watching it should be how you watch it.
But someone did post an interesting (albeit old) article by a lead at US Renditions:
Poor Voice Directing
Have you ever watched a dub and the voice sounded so out of place that you found yourself distracted from the film and concentrating on the voice? Most of the time bad acting is to blame, but not always. Sometimes the voices are just out of place. For example, consider the dub of GIANT ROBO volume 1. I know several people who think GIANT ROBO is a fine dub, including the producers of the dubbed version; I, however, do not agree.
When I first saw the dub, I was wholly unimpressed, and I was not interested in seeing any other episodes. However, when I went home that very night, a friend popped in his Japanese version for a group of us. Despite the fact that it was the exact same episode, the exact same animation, and I couldn't understand a word of the dialog, I found myself caught up in the spirit of the show. At the time I was pretty shocked that I had such a different experience, but I just filed GIANT ROBO into the "dubs suck" file and went on with my life.
Now that I am in charge of US Renditions, I have a vested interest in GIANT ROBO (which was not successful by the way), so I studied the dub and the Japanese versions in depth (I have now seen episode one roughly a dozen times). Finally, I came to the conclusion that the direction was at fault.
What is directing when it comes to voice acting? Voice directors cast the voices, choose the dialog, give the actors pointers as to how lines should be read, and generally organize the different components to fit an overall scheme. For GIANT ROBO, the voices are slightly miscast and give a campy, half-serious performance. To me this is 85% responsible for my disinterest. In the Japanese version, the acting is very serious and creates a very dramatic atmosphere that is quite appropriate for a story line where lead characters die left and right. In the campy dubbed version, the voice acting detracts from the drama and creates a cartoony atmosphere in which it is impossible to take the drama seriously and thus the conflict seems pointless. This kills the mood of GIANT ROBO, and I believe has caused the loss of about 20% of the potential sales; even worse, a whole lot of people are missing out on a terrific action drama.
How could this have been averted? Simple attention to the details, the formula for any Anime. Make sure that all of the actors, not just the leads, are not only strong voices, but appropriate for the proper atmosphere of the film.
The hardest part of all: listening to, or watching, your own work with an unbiased critical eye.
Bad Actors & Inbreeding
These two closely related issues are difficult to separate because when I say "inbreeding," I am referring to the fact that Anime producers keep using the same voice actors over and over again, regardless of quality. Part of this condition is a case of the producer/voice director becoming friends with actors (which makes objective opinions difficult), and another part is due to the limited funds and time allotted for casting the production.
This problem is compounded by the fact that most of the dubbing (65%-75%) of the American dubs are contracted to two studios: Animaze (Los Angeles) and Ocean Studios (Vancouver). Since these companies do the majority of the dubs for Central Park Media(US Manga Corps, Anime 18), Pioneer, Viz, Manga Entertainment, Books Nippan (in the past), and even a bit of DIC (Sailor Moon), the same pool of actors shows up over and over again in industry dubs. This would not be so unfortunate or noticeable if the actors had the range or the acting ability of their Japanese counterparts, who are capable of delivering extremely different performances for a wide range of characters.
Amuro Rei (Gundam)
= Tuxedo Kamen (Sailor Moon)
= Furuya Tohru
= Otonashi Kyoko (Maison Ikkoku)
= Shimamoto Sumi
Very few American voice actors - at least the ones used by Anime companies, seem to project such a varied range. (For more Seiyuu (Voice Actress/Actor) info see Hitoshi Doi's fabulous seiyuu database )
As for bad acting, this is easy to prove - simply listen to ROBOTECH ("OooOooh Rick"), NEW DOMINION TANK POLICE (especially, and tragically, the voice of Leona), or my personal nemesis ORGUSS (three attempts so far to watch Volume 1, and I never made it past episode two of three…).
These bad actors overstress emotions and do not even come close to a genuine performance. Unfortunately, most fans of dubbed Anime don't mind the bad acting, instead they celebrate the campy-ness of the bad dubs. As long as this condition prevails there will be little interest in improving the quality of acting.
Lack of Motivation
Hardest to prove, easiest to deny, but in my mind, lack of motivation is the number one reason why American dubs are so bad.
First of all, the Anime companies know that their biggest critics, Anime Fans, are hardly ever satisfied by dubbing efforts. Therefore, since they know they can't win, why should they try?
Good dubs seem to take more time and more money - both valuable commodities. Will better dubs sell more tapes? Perhaps, but it is very tough to prove, so why not crank out seven average dubs instead of five really good ones? Why not indeed? The answer invariably is to crank out the volume so the company can start selling the videos.
I can't think of any truly positive motivation technique other than sheer pride, and money seems to be an adequate salve for that injury so far. If any of you readers think you have a brilliant idea, I'm hoping the industry is open to your suggestions.