In terms of decreasing psychotic symptoms and treating acute mania, all of the antipsychotics work well. Clozapine (Clozaril) is the only antipsychotic that has been shown to have a clear clinical edge over the others (this was demonstrated in people with schizophrenia, but has not been specifically proven in bipolar disorder).
This is largely why this medication, which requires frequent blood draws due to a potentially fatal side effect in which the body stops producing white blood cells needed to fight infection (agranulocytosis), is allowed on the market. Also, clozapine and lithium are the only two medications to date that have been shown to decrease the rate of suicide.
However, clozapine, because of its side effect profile (weight gain, risk of agranulocytosis, sedation, drooling) is rarely used as a first or second line antipsychotic in bipolar disorder. It’s more commonly prescribed for people with psychotic symptoms that have not resolved with other medications, such as occurs in some cases of severe schizoaffective disorder and schizophrenia.