Anyway, I say both. Generally Japanese is better due to the fact that the anime were created with being spoken in Japanese in mind, thus there is allowed for more freedom in the Japanese (voice acting training is also a bigger deal over there, or rather, it was). Dubs, on the other hand, are only as good as the script their given, and similarly Voice Actors are also only as good as the scripts their given. For instance, I'm playing The Last Remnant and the main character is voiced by Johnny Yong Bosch, a great voice actor (he also voices Vash the Stampede and Kaneda from Akira. Oh, and Ichigo Kurosaki). Problem is, the script they give the character is so cliched and a failed attempt at capturing the contemporary audience that his own performance comes off that way. Dubs are restricted to what they're given, and they can't make any really changes without pissing someone off. Luckily, as time goes on, script writing gets better and better (Persona 4 and Summer Wars are two examples, even if the former is a game (it's probably got my favorite dub in any piece of media)), and as such, so does voice acting. Similarly, as anime becomes more prominent, people get better voice acting training, thus leading to more good voice actors.
So, in my case, I'll watch dubbed if it's available, subbed if it's not. Plus, I always go language over quality, so if there's a dubbed version available and a higher quality subbed version, I might take the subbed version. Reason being, anime is art, and I don't like to avert my attention from the show to read the text.