Water is being pressurize so it does spray harder to remove dirt, mold etc. The benefits of this is that you are able to use less chemicals when cleaning and you get a better deeper clean on certain surfaces (ie a concrete driveway). Is pressure washing safe? Yes. As with anything, if you do not use the equipment properly you can cause damage. But if you properly use a pressure cleaning system, you will have absolutely no damage to any surface and you will be able to get surfaces clean with little, sometimes no chemicals.
Water runs through a pump with no pressurization. Soft washing normally consists of a higher volume of water being sprayed from the hose rather then pressurized water. Soft washing also uses a higher concentration of chemicals or cleaning solutions when cleaning a home. Where a pressure cleaner may be able to remove some dirts with no chemicals because of the pressure, soft washing systems need the chemical to loosen the dirt before the water is sprayed to remove it. The benefit of soft washing is that there is less pressure being applied to a home but that comes at the expense of more water and more chemicals having to be used. Is soft washing safe? Yes. Just like pressure cleaning, though, if you do not use the system properly you may cause damage. High chemical concentrates can kill plant life and damage certain surfaces. Properly used, it is a safe way to clean.