I've had a kegerator in my garage for the last two years, I had a good buddy tell me when I bought it off him and bitched about headaches and bad hangovers... and he asked me, when do you most often drink Draft beer? Weddings, Grad Parties, etc... times when it's most likely open bar, and you are pounding the shit out of them. You drink them twice as fast and twice as many.
You get yourself a 12oz glass, and focus on not sucking the bottom off of them, and I don't have any difference in hangover. Busch Light in the keg or Busch in the can, no headache, but shit like a goose.
I always said that about draft beer and hangovers as well until I got mine... Who knows.....