Southpark has the deeper quality. FamilyGuy relies far too heavily on film references all the time, rather than make its own meme. its saved by a talking dog and psychotic baby, otherwise it would be a Simpsons clone.
Tough. I think I laugh out loud more at Family Guy but South Park is much cleverer and more satirical. Hmmm Family Guy only because I don't find South Park quite as good as it used to be.