I've trained myself after watching 150 episodes of Naruto in 2 weeks to read and watch at the same time, but I'd still rather not have to do both.
For me, there is only one reason I would prefer a subbed anime to a dubbed one. And thats if it was overly-edited (all blood taken out, etc), the script was overly-edited (like replacing the word "die" with "destroyed", or "kill" with "destroy"), or if the VAs sound horrible. For example, lets take an example of what I'm talking about with a dubbed anime. Lets take Naruto. I refuse to watch Naruto dubbed it sucks so much. They overly-edited it by taking out virtually all the blood, though they thankfully left in some. They overly-edited the script, replacing the word "kill" with "destroy" many a time. For example, when they were talking about Zabuza killing all his peers when he was becoming a Ninja, they used the word "destroy", and completely killed the effect. And thats a common occurance. And as for bad voice actors, Naruto sounds like a little bitch. This is reason #1.
Early DBZ suffered from that, but later on they stop taking out the blood. Hopefully they will stop screwing up the Naruto dub.
There is a difference between getting an english voice actor who sounds like the japanese voice, and getting an english voice actor who sounds the part of the character. English voice actors don't need to sound like their japanese counterparts. They just need to sound the part of their character. Some japanese voices don't sound good in english, and visa versa. VAN (Voice Actor Nazis) don't understand that.