Are you asking because you believe you fall into one of the two categories?
Anyways, "mental illness" is an umbrella term that covers so, so many states. If you ever happen to look at the DSM that psychiatrists and psychologists consult (which is regularly updated and added to) you will be floored by the sheer number of of illnesses they define. Perhaps, like me, you will be hesitant to believe that all of the listings are legitimate. At any rate, that school would probably (I'm not studied in it) classify "insanity" as a type of psychosis or mania. There are "psychotic" episodes as well as "manic" episodes. Mania can be more euphoric; a person suffering a manic episode can feel that great revelations or mysteries have been revealed to them. They can feel a sense of divine purpose or intervention even if they are not regularly religious. A manic will find themselves feeling a surge of energy from nowhere, propelling them not to eat or sleep. They say that psychosis is more of a depressive state, and can include having hallucinations or delusions. However mania and psychosis can happen at the same time, wherein a person is euphoric and energized, but also paranoid and delusional and/or hallucinating.