Really, this is a fascinating subject, as a whole. I have to agree with the fact that, at times, the English counterpart could very well surpass their Japanese respective. When it comes to an anime like Cowboy Bebop, or Samurai Champloo, one could practically feel the emotion, in Cowboy Bebop, for instance. Steven Blum really could make someone feel the role of Spike, and I still respect that.
When it comes to a company like 4Kids, they tend to, no offense meant toward the dubbing actors, butcher the anime they pick up. One Piece is the greatest point, such as when they changed every name in the series that had a remote importance. Portgaz D. Trace? If that didn't sound silly enough.
There's also the fact that, well, 4Kids seems to stereotype, if no one ever noticed. With Nico Robin, she spoke with a Southern dialect, if only because she wore a cowboy outfit. Shanks had red hair, so he was forced with a poor Cockney accent? Dracule Mihawk and his Carribean / French accent?
Guess you have to take the bad in with the good. Just be thankful when these animes are saved by people like FUNimation, that actually care about the fans.