A PPF account opened 15 years before the goal can be used for any goal. Sukanya Samriddhi Yojana has a 21 years lock-in which will make it unsuitable for UG college goals since only 50% can be withdrawn for higher education. Ultimately the choice will depend on the time left until account maturity. This is all the more reason that a PPF account should be opened as soon as the investor starts earning or even earlier as a minor.