It's a hard choice, if you include Vertigo in the choice, DC wins. As much as I love marvel, those titles it has are phenomenal. Preacher, Sandman, Hellblazer, Transmetropolitan, Ex Machina, The Invisibles, DMZ, 100 Bullets and many many more.
But if you exclude them I chose Marvel, I can't get into DC and it's continuity, I don't know where to start with all the crisis and reboots. Marvel on the other hand, while it's sliding timescale has some quirks (Vietnam becoming Afghanistan for Tony Stark), it's generally pretty fluid. The last seven years has had massive upheaval (Disassembled to Siege) in the comic world and for better or worse it's been at least interesting.
I also find their characters more human and have personality. Don't get me wrong I love a good Batman or Superman comic, but by this points they've become such big figures that I find they're diluted by so many different interpretations.