How does the whole HDB loan concept works and why is HDB loan better than bank loan?

Seedly's got a pretty comprehensive comparison: A Homeowner's Ultimate Guide: HDB Loan vs Bank Loan - Which Is Better? (seedly.sg)

TL;DR - it's hard to say which is better.

HDB loans charge more interest in the long run, but are more lenient with late repayments and give you the option of repaying in full early. Over the past decade, bank loans have offered significantly lower interest rates compared to HDB loans, but have higher penalties for late repayments and full repayments.

You can refinance from a HDB loan to a bank loan at any time, but you cannot go back to a HDB loan once you refinance.

It depends on your needs. Whatsapp me 98633966 if you wants to know more and a Mortgage Broker