While it's true that both policies are geared towards safeguarding against third party suits, they do not share any other similarities. Effectively, you need both to safeguard your business. Professional liability insurance will shield advice providing employees from bearing the full costs of litigation from external parties as well as any punitive damages in the event the said suit is found to be valid. The policy, however, does not take any responsibility for damaged property or physical injuries hence the need for GL Insurance.