A recent study was performed by researches at Brown University to compare the severity of a hangover when different alcoholic beverages are consumed. Participants in the study were healthy people between the ages of 20 and 33 that normally drank alcohol on a very regular basis.
The participants would drink a preplanned alcohol for the evening. One evening it would be whiskey, another it would be beer and so on. After the night of drinking they would fill out a survey on their hangover, detailing the severity, what symptoms they experienced and how long they lasted.
After 95 participants concluded their drinking and surveys the research team could definitely see a patterns. While the symptoms of being intoxicated were on the same level, the symptoms of the hangover state was different. Drinking bourbon or vodka did not show a difference in how drunk a person was, yet the hangover from the bourbon showed more severe symptoms.
The conclusion of the study was that the darker or heavier the alcohol, the worse the hangover was. Drinking lighter colored alcohol will get you just as drunk as drinking the darker stuff, but it will make your morning after hangover much more bearable.

Did they also control for what type of alcohol the person would normally drink? I typically drink whiskey, and if I do a vodka night the next day for me is killer. Did Absolut sponsor this?
I completely agree with the poster #1.
I am the exact same, Jack Daniels doesnt hurt me, but a night of vodka keeps me in bed the next day.