Without a doubt, I prefer anime, usually subbed. I love having the Japanese feel of the voice acting - and it's generally much, much better than the English voice-overs - but also being able to read while watching. I used to prefer English dub since I hated reading while watching, but the authentic presence of Japanese sub anime is unbeatable.
@Bold: Um, that's absolutely false.
The original and dubs are often about the same quality as the other. Sometimes the dub is better, sometimes the original is better. The only real difference between the two are the "authenticity" of the original that you mentioned and the inability to tell the quality of voices apart in Japanese and English, or whatever language a person chooses.
Authenticity... is a really flimsy argument. Just because it came from that language doesn't mean it's best in it. I mean, sure, lots of dubs end up having some corny dialogue, but the originals have it, too. It' just not as obvious to someone who doesn't speak Japanese, so it doesn't seem as bad/punny/corny.
Some original series have seiyuu that are really awful, yet people think they sound better than the dub just because they can't tell how awful it is. Off the top of my head, there are a good handful of seiyuu for the Digimon series that are just as bad as the dub casts can be. Generally, when doing something that requires will power.motivation, you should have strength in your voice, yet there are times when they're flat as hell when they're in those moment, with one serious offender coming to mind. Thing is though, in anime like that, the problem tend to exist in both the original and dub in one way or another, leveling the two out.
I'm not saying not to like subs, at all. I watch both interchangeably with a slight preference for the dub. I still try to go for the higher quality version of the two, thus resulting in watching a dub, as they're usually close in terms of quality. Unless you'e watching an anime specifically targeted at kids internationally (Digimon, Pokemon, Yu-Gi-Oh!), the dubs (At least English, though I've heard a few good reports for French, Spanish, and German dubs) have a good chance of being about equal quality with the original.
Some series, such as TTGL, Death Note, and, from what I've heard, Host Club have amazing dubs that beat out the original by a good margin. Again, not telling you which to prefer/like/etc., but don't go saying how dubs are so inferior to the original, when most times they're basically equal quality. exceptions exist, but they are not the rule.