Well the XMB is more functional, especially outside of game and particularly for media playback, the 360 is cluttered and genrally messy, but still I feel it has a more 'welcoming' feel if that makes sense.
Overall gotta prefer the PS3s menus though. Compared to the PS3 the 360s UI just feels slow and clunky. Also I don't see how you can say it's complicated... seriously it's a lot more logical in design than the 360s.