In my personal opinion its not worth balancing the extra carbs in my diet to fit in a gatorade or vitamin water when i wholly 100% enjoy water and prefer it instead. There are a bunch of research projects going on in the past few months about gatorade though. I know at www.gatorade.com
there was a whole big mess of a deal about how gatorade improved performance according to their labs or whatever.
I tend to take what a company says about the science of their product with a grain of salt...however there is a study that i did find about gatorade. Here is an excerpt and the whole study's PDF
After conducting our statistical analysis, we have found that Gatorade was slightly more
beneficial than water regarding RPE (rating of perceived exertion) and weight change during prolonged exercise. With
this in mind, we recommend hydrating with Gatorade during prolonged exercise bouts.
Individuals who would be interested in this finding include anyone who needs to stay
hydrated during any form of moderately intense prolonged exercise. This
recommendation may be especially relevant to those participating in uphill walking in a
heated environment. Groups that this recommendation may be applicable to include any
group involved in athletics or recreational activities that involve proper hydration.
HOWEVER in the same study, in their abstract they state...
Danielson , A.R., Morris, L., Neiderhauser, L., Stanek, K., Wolter, J. The Physiological
effects of water vs. Gatorade during prolonged exercise. J. Undergrad. Kin. Res. 2006;
1(1):15-22. The purpose of this study was to investigate the physiological effects of
water vs. Gatorade during prolonged exercise. Subjects consisted of 10 recreationally
active females between the ages 19 and 22. Each participant was asked to perform two
90 minutes exercise sessions of inclined treadmill walking. One session consisted of
drinking 32 ounces of Gatorade during exercise and the other drinking 32 ounces of
water. There were significant differences (p< 0.05) in peak rating of perceived exertion
(RPE) and weight change. The data suggests that drinking Gatorade during prolonged
treadmill walking under heat stress elicits lower RPE values than drinking water,
(Gatorade mean peak RPE = 4.0, water mean peak RPE = 4.9) p = .010. In addition,
weight change also shows a significant difference (Gatorade mean weight change = .134
kg, Water mean weight change = -.363 kg) p = .018. The findings in our study are
important to exercise physiology as it suggests lower physiological stress when
consuming water vs. Gatorade during prolonged activity.
What I gathered from this study, and others that I have read is that these sports drinks do provide some sort of benefit but the actual benefit is so minute and subjective that its not worth it.
Small note, yes these studies are for gatorade, and you asked about vitamin water, but I just generally thought you meant "sports drinks".