Never buy the policy based solely on the amount of your premium. See what each insurance company is charging for the premium. If one is charging less then just dont jump at the offer, as the charges of such companies are far less.
Always make your decision based on your budget. Do not opt for policies that are expensive and prove tough to be continued later. So do not go for private health insurance policy, if your budget does not permit, as these kinds of policies are too costly.