I just discovered JM after seeing The Resolution video on FNMTV last month, and I've already fallen in love. I plan on buying both albums as soon as I get my iTunes gift card.
I think what Andrew's music has that a lot of his peers lack is depth and emotion. That makes Jack's Mannequin stand out in my opinion. It's catchy and upbeat, but melancholic at the same time. Like one reviewer said, "sweetly melancholy."