It would depend on your risk taking capabilities. Remember that disclaimer you hear every time there’s an investment ad on the TV? “Investments in the securities is subject to market risk”. Reward is directly proportional to the amount of risk you take. If you are young then you can choose to invest in the markets because income from markets isn’t your only source of revenue. If you are old and are depending on a fixed source of income its better to invest in FD’s.
So it’s entirely dependent on one’s own perception and risk taking capabilities.
Another option would be to segreate funds and have it invested in both FD’s & MF’s rather than choosing a single mode of investment.