I think the project size should be already considered in realistic discount rate.
For example, the investment for A is 1000, and the investment for B is 10000. The NPV for A is 500 and the NPV for B is 501. We say although B has a higher npv, but A may be better because of lower investment cost. But the discount rate for A, for example, is 5%. And due to the risk and project size, the discount rate for B might be 30%.
So I think if the realistic discount rate for the larger size project is conservative (or accurate) enough, this disadvantage will not occur.
