Clemenza was always the louder and more flamboyant of the two caporegimes. You see this at the wedding (Tessio dancing quietly with the little girl, Clemenza loudly demanding wine) and at other meetings. Tessio is quieter, more thoughtful and introspective. Tessio's men were given the all-important job of guarding Vito at the hospital. His intelligence and trustworthiness are given in subtle ways throughout the film.