Praise be to Allaah.
Imaam Ibn Qudaamah (may Allaah have mercy on him) said: “Section: the Sunnah is for the same person to lead the prayers as gave the khutbah, because the Prophet (peace and blessings of Allaah be upon him) used to do both himself, as did his successors (the khulafa’). But if one man gives the khutbah and another leads the prayer for a valid reason, this is permissible. This is what Ahmad stated…because if it is permissible for someone else to take over leading the prayer for a valid reason, then this applies even more so in the case of the khutbah with the prayer. If there is no reason, then Ahmad (may Allaah have mercy on him) said: ‘I do not like it if there is no excuse.’ The reason why it is not liked may be because the Prophet (peace and blessings of Allaah be upon him) used to do both of them, and he said, ‘Pray as you have seen me praying’ (Reported by al-Bukhaari and Ahmad), and because the khutbah takes the place of two rak’ahs. The reason why it is permissible may be because the khutbah is separate from the prayer, as if it is two prayers.” (al-Mughni, part 2, Kitaab al-Jumu’ah: Fasl: yatawallaa al-salaah man yatawallaa al-khutbah. See also: al-Badaa’i’, 1/262, al-Sharh al-Kabeer, 1/499).
The fact that the one who leads the prayer knows more Qur’aan than the khateeb is not a reason for going against the Sunnah of the khateeb also being the imaam for the prayers. The khateeb should lead the people in prayer and recite whatever he can of Qur’aan, even if there are people behind him who know more than he does. And Allaah knows best.