Whole-of-life assurance and term insurance provide different roles for your protection needs.
Term insurance will be cheaper, because cover only lasts a fixed period of time (known as the policy term), which you can choose. It tends to be used to provide money for circumstances that have a fixed time period,. Examples include repaying a mortgage or supporting your children until they are financially independent. Once the time has passed, the policy will end and so will your premiums.
Whole-of-life assurance tends to be used for providing money in circumstances that will remain for the rest of your life. For example paying for a funeral, or providing for an inheritance or to provide funds for your family to pay any inheritance tax due on a large estate.