Sengun is the lowest on my list. I think C fans would get annoyed with him quickly. If people think Brown is inefficient, or that Tatum complains to the refs too much, wait till they watch Sengun every night. Still, KAT and the Knicks has given me more confidence in a team's ability to win a championship with a meh defensive center.
Duren and Clingan are pretty similar to me. Both a solid options with upside, but my concern is that Duren's next contract will be significantly more than Clingan's.
Mobley is the best player of the bunch. He provides the best defense overall of the bunch. One concern is that he's probably is not a full-time center. He's a solid scorer, but not high usage like Sengun. He also projects to be able to stretch the floor throughout the prime of his career. But he also would likely be the biggest contract of the bunch.