I actually prefer dubs *dodges a hail of rotten fruit*
For the following reasons:
1. I really don't like having to concentrate on looking at subtitles over what's going on on the screen. Most modern anime has very slick visuals (Last Exile, Full Metal Alchemist, Stand Alone Complex) and I want to be able to appreciate those without having to peer at text.
2. As already stated, some English VAs are very competent at what they do. (Steven Jay Blum, for one example, Richard Epcar and Crispin Freeman for another, and dare I say it Johnny Yong Bosch. Don't you -dare- judge me
He did a damn good job on Last Exile. Mike Kleinheiz does a pretty quality gig too, although your mileage may vary depending how much you like the shows he's been in)
3. Not being a Japanese speaker of any degree, I often find it difficult to distinguish between the sound of individual Japanese VAs. Thus, following a conversation between more than two characters can be a little confusing if they all sound alike. If it's an English dub following the conversation can be easier. (Explanation: I have difficulty following something if there's a level of background noise, so even if Japanese VAs sound slightly different, if there's action or engine noise f'rex on the screen then I have a little difficulty discerning individual voices. It's not a pronounced problem, but it is annoying.)
Although I do sympathise that there are some pretty crappy dubs out there. Luckily I've managed to avoid the really dire ones. I suspect that this is through luck rather than discerning choice, as I'm pretty indiscriminate when it comes to anime buying.
/Simon