Subbed, definitely. The quality is just so much better, and it only takes a split second to read so it doesn't distract at all.
99% of dubs are just..terrible. I was going through dubbed Naruto episodes recently to see how they handled scenes that would only make sense in Japanese, and it was just...wow. So bad. The script is also quite degraded and censored in most dubs. The only dub I found good enough to watch/buy DVDs of is FMA, but even then the sub is a lot better (which I've watched as well).