I vastly perfer the dub for Trigun. Johnny Bosch is Vash. The Cowboy Bebop dub is phenomenal. The Last Exile dub is great. The Heat Guy J dub is awesome.

Oh, and probably the biggest example would be Hellsing. Not only is Crispin Glover a far better Alucard than his japanese counterpart, the actual dialogue has so much more character in the dub. Example (not exactly verbatim):

Episode 1

Subtitled Alucard: I feel like sucking some blood tonight.

Dubbed Alucard: It's a nice night. I think I'll have a bite to drink.

Glover's take on it is the far better of the two, and that's something that stays consistent throughout the entire series.. Granted, most of the rest of the english cast isn't quite as awesome as Crispin (with the exception of the guy who plays Paladin Anderson), but he alone makes the dub better than the sub.