Which is better: reviving a surau with few worshippers or praying at a mosque with a large congregation?

Summary

The fatwa cites two groups of views. Al-Shirazi and Ibn Qudamah give priority to the mosque or surau with a small congregation, so that a congregation can be established or increased there. Al-Nawawi and al-Kaff state that, in principle, the mosque with a large congregation is more virtuous, except in certain situations, such as when the small congregation would cease without a person's presence, or when the imam of the large mosque is a sinner, an innovator or neglects the pillars of prayer. In its conclusion, the fatwa holds that it is better to revive the surau or mosque with few worshippers, taking the circumstances of the place into account.

Written in our own words from the original fatwa — check the source before acting on it.