As for the rational argument, some scholars have presented it as follows:

Uthmān was more knowledgeable about the Quran, while Alī was more knowledgeable about the Sunnah. Uthmān’s striving in Allah’s cause with his wealth was greater, while Alī’s striving in person was greater. Uthmān was more detached from leadership, while Alī was more detached from wealth. Uthmān was more scrupulous in avoiding bloodshed (1), while Alī was more scrupulous concerning wealth. Through striving against his own soul (2)—by patiently refraining from combat and not fighting—Uthmān attained what Alī had not attained in like measure.

The Prophet—may Allah bless him and grant him peace—said:

“The one who strives in Allah’s cause is the one who strives against his own soul for Allah’s sake.” (3)

Uthmān’s conduct (4) in office was (5) more exemplary than Alī’s. They therefore said: This establishes that Uthmān was more excellent, because knowledge of the Quran is greater than knowledge of the Sunnah.

In Sahīh Muslim and elsewhere, it is reported that he said:

“The people should be led in prayer by the one most proficient in reciting Allah’s Book. If they are equal in recitation, then by the one most knowledgeable about the Sunnah.” (6)

Uthmān had undoubtedly memorized the entire Quran, and would sometimes recite it in a single unit of prayer. As for Alī, there has been disagreement over whether he had memorized the entire Quran.