I usually default to subs, but there are certain dubs that are pretty iconic and I'll sometimes choose over the Japanese. For example I always enjoy the English-language cast of Cowboy Bebop and count that as one of the times they really Got It Right translating the dialogue and casting the dub.

And, of course, there are the gag dubs like Samurai Pizza Cats or the Funimation version of Shin Chan in which the dub clearly veering away from the source material and doing its own thing is the whole point.