Does silent dhikr count, and is it better than loud dhikr?

For those who are concerned that, if the words are not uttered by the tongue, remembrance is not valid, a hadith of the Messenger ﷺ validates the consideration of silent dhikr, as even the angel scribes cannot hear it.

It is narrated that the Messenger ﷺ said, "The silent Dhikr which even the angel scribes (al kiram al katibun) cannot hear is seventy times superior (to vocal Dhikr) on the day of Resurrection. Allah will gather all of His creation for accounting of their deeds and the angel scribes will bring forth whatever they had preserved, Allah will say to them, 'Is there anything else which is left?'

"They will reply, 'As far as we know and what we recorded, there is nothing that has been left out or unrecorded.' Allah will say (to the person), 'I have a good deed of yours which even they are unaware of, and I will reward you for it, the deed is silent Dhikr.'" [as-Suyuti, al-Budur as-Safirah; Abu Ya'la, as quoted in Majma az-Zawaid 10/81]

However, verbal utterance is unanimously considered necessary in certain injunctions, such as the recitation of the Qur'an, in Salah, in contracts such as marriage or divorce, and in many other situations. Depending on the tariqa, the shaykh may teach verbal remembrance or the silent remembrance with the heart.