While both approaches involve an expansion of the central bank's balance sheet, in  18  BIS Review 54/2009  a pure quantitative easing regime, the focus of policy is the quantity of bank reserves (liabilities of the central bank); the composition of loans and securities on the asset side of the central bank's balance sheet is incidental.
In contrast, the Federal Reserve's credit easing approach focuses on the mix of loans and securities that it holds and on how this composition of assets affects credit conditions for households and businesses (Bernanke, 2009). The Bank of England is also now doing similar quantitative easing.