A paper in the journal Alchoholism: Clinical and Experiment Research by researchers at Brown University reveals that the colour of alchoholic drinks really does affect how bad you feel the next morning. Darker drinks (such as whisky) contain more chemical by-products than do lighter ones (such as vodka). However, how you feel (in terms of hangover) does not necessary correlate with performance loss the next day. So you may feel better drinking vodka but you would be just as incapable of driving or using heavy machines etc than if you drank whisky – though the latter may make you feel worse.
See http://www3.interscience.wiley.com/journal/123216970/abstract
The Abstract Conclusion at the article’s link contradicts itself. The first 2 sentences say:
“As drinking to this level affects complex cognitive abilities, safety could be affected, with implications for driving and for safety-sensitive occupations. Congener content affects only how people feel the next day so does not increase risk.”
The last sentence says:
“As hangover symptoms correlate with impaired performance, these might be contributing to the impairment.”
So congener content does not increase risk, but it contributes to hangover symptoms (including how people feel) that do increase risk.
I won’t raise a glass to the logic used by these authors.