There's also so much more Live brings such as 'CLAN's' and then maybe a group of you meeting up and taking part in a competitive event - and you get to widen your circle of friends considerably. Talking to different people around the world can often be a pain - especially some prepubescent singing the annoying songs over and over until you boot them from the server - but you also get the oportunity to converse with people you never ordinarily would. I've had long chat's with some really nice people on there.
You're not making real friends on Xbox Live.