Is it better for the worshipper to pray the Sunnah prayer that precedes the obligatory prayer facing a Sutrah and lose his place in the first row, or to pray away from a Sutrah to maintain his place in the first row?

You can combine the virtue of the first row with taking a sutrah. If the distance between the first row and the mosque wall is three cubits or less, then pray in the first row, and the wall will serve as your sutrah. If the distance is greater than that, then take a sutrah (such as a prayer rug, a stick, or a line) while maintaining your place in the first row.