Which is more befitting and better: Returning to perform the Sunnah (Nafl) prayer before the obligatory prayer in the mosque to ensure leading the prayer and to spare the congregants those who do not recite well, or continuing to perform the Sunnah (Nafl) prayer before the obligatory prayer at home regardless of the consequences?

If it is possible to combine performing the pre-Fard (rawatib) prayer at home with arriving early at the mosque and catching the first row, then this is superior and carries greater reward. If that is not possible, then observing the pre-Fard prayer is better because its injunction precedes that of others. Jurists have made exceptions to the general superiority of performing supererogatory prayers at home: the supererogatory prayers on Friday due to the virtue of early arrival, the two rak'ahs of circumambulation (tawaf) and ihram, the Duha prayer, and the Istikhara prayer, as well as the supererogatory prayers for someone in i'tikaf (spiritual retreat) or for a student or teacher in the mosque. For these, it is better that they be performed in the mosque.