South Park: Biting, irreverent, sometimes over the line social commentary/satire. But almost always enormously funny and never preachy. Can be offensive... if you're a pansy.
Family Guy: No real point or plot. Just a string of tired jokes mostly. Their best parts are the "This reminds me of the time..." which isn't even real satire or parody, just a lame rehashing of some piece of pop culture usually. (although the Elmer Fudd / Bugs Bunny bit made me laugh)
South Park all the way. But to each their own.