1. Insulation Material: Rock wool panels are made from natural rock fibers, typically basalt or diabase, processed into rigid boards or flexible blankets. PU panels are made with a rigid polyurethane foam core material.

2. Fire Resistance: Rock wool has excellent fire resistance properties and can withstand high temperatures without melting or releasing toxic gases. PU foam is combustible and can contribute to the spread of fire. However, panels can be manufactured with flame retardants to improve their fire resistance properties.

3. Thermal Insulation: Rock wool provides good thermal insulation, effectively reducing heat transfer through the panel. PU foam provides excellent thermal insulation with low thermal conductivity, resulting in high energy efficiency.

4. Sound Insulation: Rock wool has excellent sound absorption properties, making it suitable for applications that require noise reduction. PU foam has some sound absorption properties, but it is generally not as effective as rock wool in reducing noise.

5. Moisture Resistance: Rock wool has some resistance to moisture absorption, but it is not completely waterproof. PU foam is a closed-cell insulation material, making it highly resistant to moisture absorption. It also prevents the ingress of water vapor.

6. Weight: Rock wool sandwich panels are generally heavier compared to other types of sandwich panels. PU sandwich panels are lightweight compared to rock wool panels, making them easier to handle and install.

7. Price: Rock wool panels are usually more expensive than other types of insulation materials. PU panels are typically less expensive compared to rock wool panels.

In summary, rock wool sandwich panels offer better fire resistance, sound insulation, and higher density, while PU sandwich panels provide excellent thermal insulation, moisture resistance, and are lighter in weight. The choice between the two depends on specific project requirements and priorities.