NPV and IRR which is best? Why?

Some people prefer the NPV method as superior to the IRR, because the IRR method implies reinvestment rates that will differ depending on the cash flow stream for each investment proposal under consideration. With the NPV method, however, the implied reinvestment rate, namely the required rate of return or hurdle rate, is the same for each proposal. In essence, this reinvestment rate presents the minimum return on opportunities available to you.