Another fundamental difference b/w NPV and IRR is that IRR assumes capital is reinvested at IRR value which can be different from cost of capital, whereas NPV assumes reinvestment is done at cost of capital. So for eg cost of capital is 10% and while calculating NPV for a project, implicit assumption is that reinvestment is done at 10% which is CoC. However of for same project if IRR comes at 15%, then it assumes reinvestment done at 15%.

Cheers!

Vikas