Well theres no recordings of the likes of the likes of O'Connell, Pearse, Carson, Larkin, Connolly etc... So I can only go on what I've heard.
I liked Seamus Costello & Bernadette Devlin of the Irish left.
I liked Ruari O'Bradaigh & Martin Galvin on the Republican side, I never really taught McGuinness or Adams were very good orators, good debaters but not orators. I liked Tommy Mckearney (1980 Hunger Striker).
I loved David Norris's speech in the Senate in 2014 on the ethnic cleansing of Palestinians from Palestine.