Easily Rondo. From the first moment on with the swelling, mood-setting synth, it's completely sovereign and frankly humbling in its mastery. Thick, delicious and bouncy basswork, excellent keyboard flourishes, and just a terrific, unified utilization of each and every instrument in the track brings it to an awe-inspiring level. They really knew what they were doing with the new audio format in Rondo, and Bloodlines probably displays that best.
Symphony's is worth a mention for how it dares to take the track somewhere different, as necessitated by the context of its usage in the game. It's an impressive reworking of a familiar motif to fit an entirely changed atmosphere from the original.