Is it better to revive the time between the two 'Isha prayers in the mosque to recite a larger portion of the Qur'an in prayer, knowing that going to and from the mosque takes time, or is it better to pray at home?

Voluntary (nafl) prayers performed at home are better than those performed in the mosque, based on the saying of the Prophet, peace and blessings be upon him: "O people, pray in your homes, for the best prayer is a person's prayer in his home, except for the obligatory prayers." This includes all voluntary prayers for which congregation is not legislated. Performing them at home is more private and further removed from showing off, and homes are blessed by it. It is permissible to perform voluntary prayers in the mosque, even if it is contrary to what is better.