DOORS is a legacy system developed in the previous century. It lacks Agility and due to its fragmented nature, it provides limited traceability on artifacts and subpar reporting capabilities. IBM CLM is not one product but rather a product suite with multiple separate components. The tool suite has a steep learning curve, and high installation, rollout, and operating costs.
DOORS Next Generation (which despite branding was originally not targeted at System Engineers but at IT people) is not mature enough for large distributed teams. It has no electronic signature capabilities and no Word/Excel/ReqIF round-trip – both fundamental requirements of a modern development team. Neither DOORS, DOORS NG, or IBM CLM scale well for large teams, and they offer no true horizontal scaling by means of clustering, which results in limited performance.