Despite being British, I have every season of Seinfeld on DVD. I can safely say that I vastly prefer it to Friends. I get Friends as something you can just tune into and have a chuckle, but Seinfeld always strikes me as far more subtle, better constructed.
There may only be one or two moments at which you burst out laughing in an episode, but when you do it will stick in your mind for ages, like the Soup Nazi, or the Junior Mint, or Newman's diabolical speech in the last episode. With Seinfeld, despite the episodes all being watchable as stand-alone affairs, as opposed to Friends' two or even three parters, you enjoy it more with every episode you watch - you get the characters better, you know their little neurotic quirks, and can relate to them!
Either way, big up Seinfeld, but it's cool whichever you prefer. Peace out!