There's a scientific reason why Cider gives you nasty hangovers.
I think it's to do with the level of Acetaldehyde in cider. As cider is oxidised, you get a vinegar like taste. Pretty sure this is Acetaldehyde.
Combine that with the liver breaking down alcohol into acetaldehyde, you end up with a lot of the chemical building up. This needs to be broken down, as it's a factor that contributes to your hangover (dehydration, hypoglycemia, acetaldehyde intoxication).
Alcohol > broken down by alcohol dehydrogenase > forms Acetaldehyde (can give hangover) > broken down by Aldehyde dehydrogenase > forms Acetic acid which is used in the Kreb Cycle and gotten rid of.
Basically, depending on your level of alcohol dehydrogenase and aldehyde dehydrogenase, you may be able to drink a huge amount more if you can get rid of the acetaldehyde, or drink a lot less if you are unable to break it down.
High levels of alcohol dehydrogenase + low levels of aldehyde dehydrogenase = alcohol intolerance!