this will depend on the person and the cycle. And it can change over time as your needs (due to aging, upregulation, hormonal exposure) change.
generally reccomend aromasin and AIFM. Generally reccomend against arimidex, though some will swear by it. Letrozole is a good option for those that need high level suppression, however for many it is just too strong causing estrogen deprivation related side effects (joint and libido issues being foremost)