Although I probably like Her better overall, 12 Years a Slave is an excellent choice for Best Picture.
It’s also worth noting that it the first major Hollywood production to deal with slavery in a serious way came out in 2013. And no, Amistad was not a serious depiction of slavery. Can we aim for 2 major Hollywood productions dealing with slavery in the second century of film? Even a meh biopic of Frederick Douglass?