Come on now, google xbox live problems:
Results 1 - 10 of about 1,260,000 for Xbox live problems.
Results 1 - 10 of about 3,170,000 for steam problems.
It does'nt take a fool to understand that there are problems with steam, esp when Valve themselves have admited so. This is just like the stutterbug for HL2, it took months for some people, with top of the line systems, to play the game at a reasonable frame rate, or without hicups. And you know what? Valve even admited there was a problem with thier software.
Steam has more problems then Xbox live. When have you heard of an actual software problem with live?
They might be down to upgrade servers and what not, but they have never had any serious bug, like problems with the friends list not working, voice chat etc.