Historically ibuprofen has lasted the longest in my 2 yr olds system.  with this virus or bacteria and ear inf tylenol (acetaminophen) is working better. Reason? Why?

Depends. It really depends on the symptoms that you are treating and what is causing them.
No One Knows. A variety of factors are involved involving the immune system, the specific infection and the child's overall health. Why in this case, is unknown.