Ok so, to me, subs are always vastly superior. However, there have been a few shows where the dub was so amazing that it couldn't be watched without the dub.
Those shows are:
Cowboy Bebop
Eden of The East
Baccano!
Trigun (the dub here is just preferred, it's not amazing or anything)
Black Lagoon
Lupin III: Castle of Cagliostro
Samurai Champloo
Steamboy
That being said, those are only about 15% of the shows I've seen, so I still VASTLY prefer subs, but when a dub is good... it's amazing. Especially for eden of the east, the dub added 20 levels of depth to the characters that the sub couldn't do. Highly recommended.
Those shows are:
Cowboy Bebop
Eden of The East
Baccano!
Trigun (the dub here is just preferred, it's not amazing or anything)
Black Lagoon
Lupin III: Castle of Cagliostro
Samurai Champloo
Steamboy
That being said, those are only about 15% of the shows I've seen, so I still VASTLY prefer subs, but when a dub is good... it's amazing. Especially for eden of the east, the dub added 20 levels of depth to the characters that the sub couldn't do. Highly recommended.