Family floaters are usually cheaper for a given sum insured, since the premium is based on the eldest member's age but shared across everyone, and they're administratively simpler — one policy, one renewal date, one premium payment. The risk is that if one family member has a major hospitalisation, it can eat into the shared sum insured, leaving less cover available for everyone else for the rest of that policy year.
Individual policies avoid this shared-pool risk entirely — each person's claims are independent — but cost more overall, since you're essentially buying multiple policies instead of one. They also make more sense once family members are considerably spread out in age, since combining a 65-year-old parent and a 25-year-old child under one floater often means paying a premium based on the older member's risk profile for everyone.
A common middle ground many families use: a family floater for the immediate nuclear family (spouse and children, who are usually closer in age and lower risk), with separate individual policies for parents, whose healthcare needs and costs are typically higher and more independent.