I think what would be a more reasonable comparison (and perhaps what Steve was implying) is whether it would be beneficial to stop and take a drink or to continue straight through a drinks station without taking a drink at all...
In which case i'd say it very much depended on your time running and also weather conditions. As we all know dehydration is baaaaaaaaaaaaad, and even slight dehydration can have a large impact on performance. For me though I certainly won't bother drinking anything during a 10k (or less) and only drink perhaps at one drinks station on a HM (unless it's hotter). In either case I never stop to drink, I do my best to drink as much as possible form the plastic cups. As runningfox says, it's a darn sight easier when bottles are on offer!
It may be biased to say it, but I think the lesser fit people may benefit more from stopping to drink, not only from taking on the fluids but the chance for a quick breather too, as you get higher and higher up the field, it'll become harder and harder to pull back those elusive seconds lost by stopping for water.
My 2p's worth anyhow
