i actually like the live version on "I Might Be Wrong" mini-album best. In fact, there are a few songs on that CD that I prefer over the album versions, like "Like Spinning Plates" and "Everything's in its Right Place." to me these versions sounds like they have so much more effort and prescese than their studio counterparts.
But to answer your question, i'd choose the Kid A version. the Amnesiac version was too way out for me.
What's Radiohead's best b-side? I'd have to choose "Banana Co" for Pablo Honey era, "Talk Show Host" for The Bends, "Polyethelene Pts. I and II" for OK Computer, and "Cuttooth" for Kid A/Amnesiac. "Kinetic" is awesome too.