Fundamentally, there is no difference as it is usually more a matter of company philosophy that may determine the title. For example, I have had positions of Purchasing Coordinator, Purchasing Facilitator, Senior Buyer, Manager-Sourcing and Corporate Purchasing Manager in Japanese and US owned companies and in all cases was responsible for Strategic Sourcing, Purchasing, Procurement, Supply Chain Management, etc. Right now I am Corporate Purchasing Manager and my strategic vs tactical tasks vary from week to week.