I love both, and everyone's least favorite episodes of The Office are actually amongst my all time favorites !
However, I've been watching Friends since I was a child and have probably seen the entire show WAAAAY more times than I can ever count. The reruns were always on when I was young and avoiding sleep.... The Office I've only watched through around three times, which is still a lot, but nowhere close to Friends.
I don't find either particularly funny though, I loved Friends for the same reason I love any sitcom. It's a story/drama surrounding a group of people and their venture throughout life. The Office was definitely hilarious in the first couple seasons, when it was more awkward/cringe based, but after that it gets very over-the-top and also focuses on relationships and the growth of the characters more. That's when it starts to stray from the original UK humor and goes to more of an American style. So, ends up being likable for the same reason most sitcoms are.
TDLR; Friends just doesn't get old...While The Office is only worth rewatching the first couple seasons.