The album or the track of the same name? 'Cause Lights was a great album and Lights was a great track but I loving love Dawn.
I suppose both. :p
I'd have to say Lights is my favorite track off the album though. I've only just discovered him and haven't really branched out into his other releases yet, but I bought the full album the moment I first heard it. The lead-in at the end of Firmament, the lyrics, the delivery of the vocals... I just love it, even if it is a tad repetitive.
I love Dawn too, but it didn't have the same impact on me as Lights. Personal preference I guess. ;)