I have no preferences about Subs or Dubs, but I would love to express my opinion on this two interesting variations.
Firstly I don't really watch Dubs except when i am bored and I join my little sis watching some morning anime session. What I notice straight away with dubs is that there are points in time where they deviate from the original dialogue! They done it on purpose? or they just can't express what the original author trying to say? Not only that, but as some members stated before, some sequences in the anime are 'redrawned' or 'censored' which "originality" just isn't there anymore. That is the reason why fansubs sometimes continue licensed series... and I think thats what fans call "Butchering"?
Also, this raises up in nearly every single post, its about the VAs (Voice Actors). I do have respect for all English VAs, but complain about the organisation/selection skills of the organisers. I have seen and hear some dubbed series where characters personality seems to flipped into another character. In japan, anime/movie/CG VAs had always been regarded as one of the important element to a successful product. I guess in US that isn't always the case, 'profit before entertainment' is their main element (I think?). If dubbing companies want to earn large profits or big support, one idea is to start VA schools like Japan. Train up not only the VAs but also the english VA organisers.
I have friend who are currently in Japan doing voice acting as part of her certificate (degree), and one of their unit is about breaking their emotional barriers and fully portraying character's emotion when doing their recordings. And thats what I found quite often with English VAs, they tend to hold back their character's feelings.
Subs are a good way of learning other languages (IMO), no matter if it is fansubs or official subs. I feel that subs are closer to the story than dubs however the reason people hate subs is because they have to read and miss out whats on the animation. But that can practise and eventually it will come naturally!
But why would I care when I can read/listen to Jap and enjoy things at their original condition.

Thats just my 2 cents...
Jam it back in, in the dark.