Moore and Morrison are both great. There's no reason to fight, children.
I'd argue that We3 is as good as Watchmen, though not as influencial.
I'd also argue that Moore is way, way better at fucking shit up. Promethea? Tom Strong? Hell, even Black Dossier sucked.
Morrison hits at least a solid triple almost every at bat. He's the better comics writer.
But Moore's the better magician. FACT.