justify the increase in expenses over the 15 years. Note that in our example, only an equity investment in Case 2 gives you a corpus which is sufficient to beat inflation.
This is not to say that you must invest only in equity instruments. Equity, as you know is high-risk and you must not invest your entire corpus in this. You can choose to have a mix of high quality debt instruments as well as equity, to match your risk-return expectations. Remember to invest wisely by keeping in mind the inflation factor, which is the most important determinant in financial planning.