God can choose to use both.
Remember St. Paul's "I become all things to all men, so that I might by all means save some" and then recall that he adjured us to "become followers of me, as I am of Christ" -- meaning, that Christ uses all mechanisms to save us.
Grace may be transmitted through a jackass, a bronze snake on a pole, words from a person, a handkerchief, a bright light from heaven, or the voice of God speaking to your heart.
Cheers!
Perhaps it's semantics, but there is only one "mechanism" by which God dispenses saving grace -- faith in His Son as Lord, King and Savior, made known to us through the Scriptures as we are guided by the Holy Spirit.
Hath in these last days spoken unto us by his Son, whom he hath appointed heir of all things, by whom also he made the worlds" -- Hebrews 1:1-2"God, who at sundry times and in divers manners spake in time past unto the fathers by the prophets,