Yes, it may be possible to give preference to their wording over that of the former two, since reports from one of them—al-Muharibi—differed, as mentioned above. Thus, his narration that accords with theirs lends greater weight to it than does his other narration, which agrees with Ibn Numayr alone. However, further evidence will come that supports this narration and gives it preference both in terms of transmission and critical analysis.
I found another route for the hadith by which a preference could have been made, were it not that the narrator himself hesitated over this very wording. Ahmad recorded it (2/67) through Zuhayr, who said: Abu Ishaq narrated to us from Mujahid, from Ibn Umar, who said: “I was sitting with the Prophet, peace and blessings be upon him, and I heard him seek forgiveness one hundred times, then say: ‘O Allah, forgive me, have mercy on me, and accept my repentance. Indeed, You are the Ever-Accepting of Repentance, the Most Merciful’—or: ‘Indeed, You are Acceptor of repentance, All-Forgiving.’”
I say: Abu Ishaq was al-Sabi‘i. He was trustworthy, but practised tadlis, and moreover became confused in his later years. Zuhayr—who was Ibn Mu‘awiyah ibn Hudayj—narrated from him after this confusion had occurred. Thus, he was the one who hesitated over this wording; furthermore, he made the general seeking of forgiveness occur one hundred times, while seeking forgiveness with this supplication occurred only once.
I also found a third route for the hadith, likewise recorded by Ahmad (2/84), from Yunus ibn Khabbab, who said: Abu al-Fadl—or Ibn al-Fadl—narrated to us from Ibn Umar, “that he was sitting with the Messenger of Allah, peace and blessings be upon him, who said: ‘O Allah, forgive me and accept my repentance. Indeed, You are the Ever-Accepting of Repentance, the All-Forgiving,’ until the person counting had counted it on his fingers one hundred times.”
I say: This is a weak chain of transmission. Regarding this Yunus, al-Hafiz said: “Truthful, but makes mistakes, and was accused of Rāfiḍism.” And “Abu al-Fadl, or Ibn al-Fadl, is unknown.”
I say: Although this chain of transmission is weak, it is an acceptable supporting witness that lends weight to the narration