I think bipolar I is more serious for several reasons. For example, when I am manic I am psychotic, have delusions of grandeur, think I am invincible and think I can fly. One of these days I just may try. Additionally, bipolar I people can have mixed states where they are both manic and depressed at the same time. This means that someone may feel like killing themselves and will have the energy to do it.

By definition, bipolar II people only experience hypo-mania which can be feelings of euphoria, iincreased energy, racing thoughts, and little need for sleep By definition, bipolar II people do not experience delusions and hallucinations.

Biplar I people, as compared to bipolar II people, have a wider range of symptoms which may lead them to do something that is dangerous to themselves or intentionally kill themselves.