Is congregational prayer Sunnah or obligatory, what is the most prevalent opinion among the people of Sunnah, and why the preference if it is obligatory?

Congregational prayer is obligatory, according to the soundest opinion. The hadiths that highlight the superiority of congregational prayer over individual prayer do not indicate that it is merely a Sunnah, but rather confirm the validity of the individual's prayer. Islamic legal rulings are derived from the totality of evidence, not from a single proof. The evidence points to the obligation of congregational prayer, and this is further supported by the Prophet's — may Allah's peace and blessings be upon him — great emphasis on it.