They're all pretty different, and his stuff is extremely preference-based so it's hard to judge whether they'd be good for one person. But I'd recommend Ghosts. It's just a really weird fucking album, and a lot more interesting than the other two. Sometimes I hate it, and sometimes I love it. It's very random, and worth it just to have when you feel like it. The other two are more standard NIN.
And I'm sure you know, but here's the
The Slip and the free
1/4 of Ghosts.