Which is better for a hangover: ibuprofen or acetaminophen?

Neither one. Acetaminophen is not good for a hangover b/c it can be toxic in high doses to the liver which may already be impaired after metabolizing alcohol. Ibuprofen is less injurious to the liver but increases the risk of GI bleeding which goes up after drinking alcohol. The best treatment would be to rest & drink plenty of fluids including water and electrolyte sport drinks.