When it comes to managing your requirements and designs there really is no contest between a manual based system and a tool based system. A cross referenced and baselined design in Cradle is your ultimate goal.
A manual based system at worst is a set of paper requirements, managed in folders with paper-clips and sticky notes. An electronic system may include a number of word processor documents, drawings and spreadsheets. These have very limited, or manually updated meta data to describe how they interlink.
A Requirements Management and Systems Engineering software tool brings these elements together in one place and provides the meta data and traceability that binds them together into a successful project.