I actually read both of them last summer (and was just talking to somebody about them yesterday). I, too, was impressed with the scope of John Henry Days, which I quite enjoyed. I was far more compelled by The Intuitionist, however, in its play with the — would it be a metaphor? — of the elevator realm, in its play of postmodernist motifs (the ideological nature of empiricism, for instance) against a backdrop almost ruthlessly modernist, and in its attempts to imagine Lila Mae’s otherness from multiple perspectives, making the book about (as Val Smith would say) not just race, not just gender, but both, and more.
But it could just be that The Intuitionist played into stuff I was already thinking about. John Henry Days was great, but didn’t really intersect so much with the things already in my head.