Ability to run multiple point clouds or meshes in a single project offers you an option to timeline your projects and visualize the progress on construction site, open pit mine, stockpile…
You also have the option to compare two or more different surfaces and calculate out volume differences almost with no limitations. You can compare the difference between realistic and designed surfaces or combine new surfaces based on different data sources.
Another benefit that multiple data types and data layers gives you is that you can define your final result based on combined data. Use Photogrammetry results on open areas and Airborne LIDAR on forest areas and design the best possible surface model for terrain visualization.