Seinfeld and The Simpsons peaked at the same time so it is hard to separate them, and you're right that animated shows can get away with a lot more. Seinfeld did get away with a fair amount of stuff for a NBC mainstream show though.
I know I'm biased but I think Seinfeld was slightly better than The Simpsons between 1991-1994. I'd say Frasier was better than both from 1996 onwards as well tbh.
Not that there's anything wrong with The Simpsons dominating the '90s...