How can one reconcile following the Prophet (peace be upon him) in performing eleven units of night prayer with completing the prayer with an Imam who prays twenty units in Ramadan? Is it better to pray eleven units and then leave, or to complete the prayer with the Imam to gain the reward of performing the entire night prayer?

Whoever desires the reward of standing in prayer for a full night should remain with the Imam until he departs, due to the hadith (definition): "Whoever stands with the Imam until he departs, it will be recorded for him as standing a whole night in prayer." This does not contradict the fact that the prevalent practice of the Prophet, peace be upon him, in his night prayers was eleven rak'ahs, as the hadith of Aisha in Muslim indicates that he used to pray thirteen rak'ahs, which demonstrates the permissibility of increasing. Therefore, there is no harm for one who wishes to leave before the Imam, but whoever desires the complete reward should remain with him until he departs, whether the Imam prays eleven rak'ahs or more.