Yes, the territories would benefit economically and socially by being French, rather than by re-joining Germany, because Alsace Lorraine has been historically French for a long time. Since World War I, Alsace Lorraine has been part of France. That has been longer than most people who live in the region have been alive. These people should continue to be French.
Alsace and N.E. Lorraine territories were once German, when Bismarck's army took this region, but in truth they were only taking back what had been taken from the Holy Roman Empire in the days of the French monarchy. This was overlooked at the Treaty of Versailles. The Allies of WW1 decided to return the region to France. Germany never got to negotiate the treaty but had to forcefully retake in World War 2.