Which is better: shortening the prayer at home or completing it with the congregation in the mosque when temporarily residing in a country during travel?

Congregational prayer is obligatory for a Muslim, and it is not permissible to abandon it except for an excuse.

If a Muslim travels and arrives in a town, he must pray in congregation at the mosque and complete the prayer; he should not shorten it, because his ruling is like that of a resident. As for on the road, it is permissible for him to pray individually and to shorten the four-rak'ah prayer to two rak'ahs.

The traveler's prayer is two rak'ahs from the time he leaves his town until he returns, unless he prays behind a resident Imam, in which case he must complete the prayer.

Congregational prayer does not fall away for the traveler, and he must attend it in the mosque if he hears the call, unless he is far away or fears missing his companions or a specific travel-related interest.