It is difficult to choose a "best" track on the score but here's my analysis and decision:
First of all, I choose "The Great Migration". I felt this piece of music was a powerful combination of unique theme introductions and stand-alone listenability. I was very torn between "The Great Migration" and "Sharptooth and the Earthquake" especially because they are both generally fairly intricate and interesting. I however, felt that "Sharptooth and the Earthquake" suffered in depth in the final bit of the track. It could have been more, whereas "The Great Migration" was enough.
(I'm writing a detailed analysis of the LBT soundtrack, thanks to this topic.) B)