I tend to watch the same series in both. >.> I'll watch the Show as it's Premiering Subbed and then when I finish it ill go back and watch it Dubbed.
That being said there are shows like Negima, Durarara and others that there is background things you almost certainly will miss if you watch Subbed only.
I can rarely watch anime dubbed anymore.
The anime i do watch dubbed i only do so because they were my favorites growing up.
For all the other anime i watch i've just gotten used to subs, the emotions/voices sound more believable in the shows native tongue.
It depends really, I prefer dubs so I can look away and still understand what's going on. Sometimes I can't stand the original dubbing sometimes I can't stand the other types dubbing.
Dubbed is nice because im a busy guy so I can do other stuff while I watch its that or learn Japanese lol (or not watch anime which is a boring thought)
I personally im unable to like English dub for various factors.
First off, they change the openings to their shows, maaaany times they do and usually its a rap or something similar.
Second, it feels as if the dubberd were emotionless, when they speak I feel nothing from them, who knows, maybe in Japan thr watchers are the same over anime and are like "gosh no Japanese would ever speak like this" but Im not japanese o judge the original source, so I will stick to it
I do have to say, I gotta support the English dub. Even though most eng dub has pretty cringe acting, there are some gems among them. They end up becoming part of characters we know and love. And eventually even show up at conventions. XD
Otherwise eng sub all the way.