Horatio epitomizes the faithful friend. He only questions Hamlet's judgment once, when Hamlet confides the fates of Rosencrantz and Guildenstern. Otherwise, Horatio supports every rash decision Hamlet makes.
Horatio is the man Hamlet wants to be. He is intelligent, but not driven by his intellectual creativity. Horatio seems to accept the world as it is handed to him where Hamlet is driven by his impulse question all apparent truths. (What T.S. Eliot calls "the energy to murder and create" in "The Lovesong J. Alfred Prufrock," a poem in which the the title character, paralyzed by words and feelings protests, "I will not be Prince Hamlet.") Marcellus and Bernardo Marcellus and Barnardo admire Horatio's intellect enough to want his opinion about the ghost, but no one accuses Horatio of talking or thinking too much. He can follow Hamlet's elaborate wordplays, but he is not inclined to engage in any. He knows enough to value what ignorance he has that can protect him from political ruin, but neither ambition nor deceit determines his loyalties.
Horatio loves Hamlet so much that he would rather impale himself on his own sword than live on after Hamlet's death. Hamlet passionately demonstrates his own deep love and admiration for Horatio in his request that Horatio tell Hamlet's story. Hamlet trusts his friend enough to leave him the task of finding the words that will divine the truth. For Hamlet, entrusting the task to Horatio declares his love better than expressing that love through any of Hamlet's poetry or philosophy. Action has at last spoken louder than words.