Well, internally, Win7 is much better
They rushed Vista out, so alot of functionality that was SUPPOSED to be in the OS Kernel, ended up as addon system-level apps running in the background.
This swamped the schedulers and if a 'piece of Vista' crashed, then you lost functionality, things 'didn't quite work right', etc.
They got it all right in Win7. It runs superb and I will finally say, better, than XP
Not only that, but Windows Server 2008 shares the EXACT same codebase as Win7, Finally.