It depends on what you're looking for in a gaming system.
Right now, the XBox 360 has a better library, but that won't matter because the PS3 will eventually catch up.
If you're looking for next-gen DVD player, it's a wash, too. Getting an XBox equipped the same as a PS3, you're looking at the same price either way. So that 1080p might be nice.
Graphics are relatively a wash, as well. IMO Sony has more room for growth, but at the moment visual quality is a tie.
As everybody knows, I prefer Sony. Simply because XBox doesn't have Gran Turismo, Final Fantasy, or a number of other SCE-designed games.