I often hear that it is more important for you to know how to do a question inside out above doing multiple numbers of questions. I have also recently heard that it is important to do as many questions as possible. Given time constraints, should I lend more weight towards quantity of questions or quality of work?

I have almost finished the questions in the Official Guide and have a wealth of practise material with Kaplan but I was wondering whether or not I should buy some more books by other providers (e.g. MGMAT or Princeton?).

Thus... Quality or Quantity, which is more important?