Soft washing and pressure washing solve different problems. Pressure washing uses controlled water pressure to lift soil and growth from durable flat surfaces such as concrete and many pavers.
Soft washing relies on an appropriate cleaning treatment, dwell time and a lower pressure rinse. It is commonly better suited to painted walls, cladding, render and many roof cleaning situations.
The surface, not the machine, should determine the method. Coating condition, material, access, organic growth and surrounding plants all need to be considered before work begins.