This standard provides a simple methodology for safeguarding control systems for development (including software).
The special feature here - in contrast to the other functional safety standards - is that aspects of hydraulics, pneumatics and mechanics are also taken into account. All other standards focus purely on electrical/electronic systems and their development.
Likewise, the evaluation of risk assessment is different (Performance Level instead of Safety Integrity Level), and the determination of failure rates is based on different approaches.
Furthermore, ISO 13849 does not have comprehensive requirements for quality management and the product life cycle, such as IEC 61508.