The main competitive feature of 3dagogo marketplace they list is that the models are tested to give reliable 3d prints.
https://www.3dagogo.com/
Update (5.2.2014):
they released a new feature: Communities:
http://diy3dprinting.blogspot.com/2014/02/3dagogo-releases-communites-feature.html
Update (26.4.2014.):
3Dagogo released AstroPrint remote and wireless 3d printer control platform:
http://diy3dprinting.blogspot.com/2014/05/astroprin-wireless-3d-printing-platform.html
"An informal survey we conducted revealed that up to 70 percent of free 3D designs on the internet are severely flawed and would result in a failed print and wasted filament," said Drew Taylor, CEO and Co-Founder of 3Dagogo.
https://www.3dagogo.com/
Update (5.2.2014):
they released a new feature: Communities:
http://diy3dprinting.blogspot.com/2014/02/3dagogo-releases-communites-feature.html
Update (26.4.2014.):
3Dagogo released AstroPrint remote and wireless 3d printer control platform:
http://diy3dprinting.blogspot.com/2014/05/astroprin-wireless-3d-printing-platform.html