Definitely Man in the Music. It goes very in-depth and is quite a good read with tons of great pictures. It also nods at multiple unreleased songs; there's individual sections about Michael's post-2005 recordings and his classical album in the last chapter as well. I haven't even read Bruce Swedien's book yet, to be honest, but I probably will check it out for Christmas.
There aren't many bad things about Joe Vogel's book, but one of them is that it really hypes you up for Michael's unreleased material. For instance, Joe reveals that Michael recorded around 100 songs for the Dangerous album. Most fans will automatically think, "Michael has 100 releasable songs from the Dangerous sessions alone! We have unlimited material!" He doesn't really make it clear (for the most part) that there are dozens of songs that are unfinished. Not to mention that he praises multiple unleaked/unreleased songs, which makes me extremely jealous that I don't have them. He also has a few facts wrong, but no Michael Jackson book is going to be perfect.
Joe Vogel's book gets a 9.5/10 for me. Definitely the better choice.