3) PPF and NSC are not similar
Another mistake individuals tend to make is to think of the Public Provident Fund, or PPF, and National Savings Certificate, or NSC, along the same lines. Granted, both offer tax saving benefits under Section 80C, both are backed by the government, and both offer assured returns, but they are very different in their structure.
On the point of liquidity, NSC scores simply because of the lower lock-in period. The NSC VIII Issue is for 5 years and the NSC IX Issue is for 10 years. PPF is much longer at 15 years and can even be extended by a block of 5 years on maturity.