There isn't a definitive answer to the question of which fraternity is the "most popular" in the Philippines. Popularity can vary greatly depending on the university, region, and even the specific year. Furthermore, the concept of "popularity" can be measured in different ways (membership numbers, social media presence, perceived influence, etc.), and reliable, comprehensive data on fraternity memberships across the entire country isn't publicly available.
While some fraternities may have a stronger presence or higher profile in certain areas, claiming one is definitively the *most* popular would be inaccurate.