"Ibuprofen, sold as Motrin or Advil, is chemically similar to regular aspirin and functions in a similar way. In lower doses, ibuprofen seems to irritate the esophagus and stomach lining less than aspirin and naproxen. If you have ulcers or acid reflux disease, ibuprofen may be the best product for pain clearly resulting from inflammation (arthritis, sprains, sunburns, etc.)."
"Acetaminophen, sold as Tylenol, lowers fevers and soothes headaches effectively, but it is not an anti-inflammatory substance. As a result, it won't do much for arthritis or sprains. It is less irritating to the lining of the stomach, making it the best headache treatment for people with acid reflux disease, ulcers, and the like."