Thriller - just too many epic songs like Beat It, Billie Jean, Human Nature, Wannabe startin something, Thriller etc. That album and those songs made Michael into the legend he became. Before Thriller he was merely another star with several hits and a big selling album. OFTW is great don't get me wrong, but its not an album that changed music like Thriller did.
Plus the weak moments on OFTW are much lower than the ones on Thriller. As funky as OFTW is, it suffers from a 1970s disco mould, Thriller is diverse with its styles and the music still sounds fresh 40 years later. I listen to Billie Jean, Beat It and WBSS all the time, but on the other album, its really just CSTYGE, Rock with You, and Workin day and night that get occasional listens.
So Thriller for me and I am sure many other people will say the same thing. OFTW was a very strong and funky album, but Thriller was a movement!
Yet if I had to compare Thriller to Bad or Dangerous, it would lose their as those 2 albums were the peak.
Thriller. While there are good songs in OTW (Rock With You, Get On The Floor, Burn This Disco Out) the other half of it sounds outdated, songs like Girlfriend, It's The Falling In Love, I Can't Help It don't sound very good these days.