From a translation perspective, neither is accurate generally.
I've seen this first-hand, because I speak 3 languages, and have seen dubs and subs for several shows in multiple languages.
When dubbing, you have to account for the mouth movements, (though frequent abuse is made of the fact that you can't always see the mouth of whoever is talking.)
With subtitles, you're functionally limited in that you can have no more than about 2 lines of text, and it has to be onscreen fairly long to be readable by the majority of people.
Both result in garbled translations that are quite humorous if you know both languages.
Neither is actually truly reflective of the 'original', and it's especially galling when you see subtitles with blatant factual errors (such as saying 200 km is 140... - It's happened. The discovery channel subtitles can be atrocious. )
People who think subs are more accurate really probably don't know what they're talking about.
Sometimes they are, sometimes they aren't.
Personally, I will watch any option available just for the hell of it.
On the other hand, if we're talking Anime, I currently prefer to watch Japanese without subtitles, which is obviously, neither. - You actually have to pay attention to what's being said to pick up anything at all like that...