Sometimes the insurance company will require the individual to get a physical before setting the rates for a policy. they then can put the applicant into a risk pool based on existing or past health problems, lifestyle, blood pressure, cholesterol, along with age and sex.
When an employer offers for free life insurance policy the insurer doesn't require a physical they just assume that you will fit into the general pool. Some people will be better than average, and others will be worse, but it will even out. some companies insurers do require physicals if you go beyond the free level, or want to increase the coverage.
If an organization is offering a group policy, that means that they have negotiated a deal with an insurer. Is it a better deal? That depends on if you individual policy is in the high risk pool, If it is the group policy might be cheaper.
Is it a better deal will also depend on the length of the term; the maximum amount you can get through the plan; can it be cancelled; and how much is of the fee is going to the organization.