What are the differences between electrostatic fixtures compared to vacuum fixtures?

The electrostatic force is uniform across the electrodes surface whereas the vacuum force is mostly active at the channels or holes. That is the reason why the electrostatic force is more stressless for the substrate compared to vacuum, which is especially true for ultra-thin and sensitive substrates.

The strength of the vacuum force is far higher compared to electrostatic forces which makes it easier to lift heavier objects. Electrostatic chucks or carriers can be used in a vacuum environment, which is not possible for vacuum chucks.