Whatever their status was in their immediate creation, and some would argue that Satan/Lucifer/the devil was of a higher and thus more powerful choir than the Michael the Archangel, who was one of the lower choirs, all that theological speculation is moot. Because St. Michael was and is faithful to Almighty God and thus was able to defeat the devil (Rev. 12:7-9). And in the same Lord God he maintains power over Satan for all those who faithfully seek his angelic intercession.
Of the fallen angels, Scripture refers to Satan as their leader, as in “the devil and his angels” (Matthew 25:41). Because of his demonic leadership, many theologians have reasonably argued that the devil is an angelic seraphim or a cherubim, though others have disagreed.
In any event, again, the devil’s pre-fallen status is a moot point. St. Michael is undoubtedly more powerful than the devil is, given his fidelity to God, and as was first illustrated in his role in vanquishing the devil and his demonic confreres from the heavenly realm.