+2
It was a strange dichotomy that most people either liked one or the other, but few liked both.
I come down in favor of Seinfeld.
I don't know a whole lot about Friends, but the characters always seemed rather "normal" or average (and thus not all that interesting, although, as a kid, I wanted to be a paleontologist like Ross).
The Seinfeld characters seemed far more quirky and almost bordering on pathological at times (as the last episode seemed to try to point out by accusing them of being sociopathic). The situations on Seinfeld, although often unrealistic, seemed far more outrageous yet still relatable. The themes of Seinfeld seemed to be about neuroses, how to navigate social norms and how to interpret the intricacies of social interaction.
Again, I'm not as familiar with Friends, but to me the situations seemed very typical of TV comedies at the time, while Seinfeld seemed different - like it was catering to a less-secure segment of society that was always questioning whether their thoughts & behaviors were appropriate to the modern norms.
I will agree there was something of a repetitive nature to the Seinfeld comedy, yet for fans it never seemed to grow old. As far as redundancy, it seems very evident if you watch Curb Your Enthusiasm, where Seinfeld co-creator Larry David recycles numerous jokes, plots, tropes, and situations from Seinfeld.