Oneness Pentecostals are not Arians. Arians (and those in their orbit) believe J*sus is a lesser being than the Father, a "demigod." Oneness Pentecostals believe there is only one person in the G-dhead and that J*sus is it; ie, when J*sus was on earth, heaven was vacant.
So would you characterize them as more Sabellian or Modalists?