MOF and ITIL aren't mutually exclusive. They are both ITSM frameworks and can complement each other quite well. ITIL provides a comprehensive service landscape over 34 practices. MOF, on the other hand, has a smaller scope, but its unique selling point is the focus on Microsoft environments.
MOF can join and improve ITIL by creating a best-practice process matrix for getting the most value out of a Microsoft-centric IT infrastructure.