well, i watched Space Dandy subbed. i think it's pretty much a toss-up, quality-wise. i think i prefer Meow in Japanese, Dandy in English (he just comes across as more comicaly melodramatic), surprisingly the narrator in Japanese, and QT's probably gonna depend on how the autotune grabs you (i like it, so English for me but other than that they're basically the same). i found Honey kind of annoying in Japanese, honestly.
however, i don't think there's any question whatsoever that the dialogue in English is MUCH more clever and amusing. which really doesn't surprise me since Patrick Seitz wrote the dub script, and he helped work on the one for Steins;Gate. "i can't read circle." "don't you judge me, you're covered in hair." "don't be cheap, dude, fire it up." stuff like this really doesn't have an equivalent in the subs, so i'm firmly in the dub camp personally.