I dunno, they both look pretty good :P I'm going to give the edge to Heavy Rain on this one, but I dunno... I just don't know enough about either @_@ And to be honest, neither one of them is on my "must grab" list. As of now Alan Wake seems to be targeting a genre that's familiar, where as Heavy Rain is trying something new. Depending on execution either one could be "better".
But they both look pretty!
From 0 to KICKASS in .stupid seconds.