i know you didn't make it up - but I'm not a fan of generalised statements that rubbish other services
in essence soft washing would last longer than 'just' pressure washing, but that really is only half a story - we would pressure wash those steps because the use of soft washing on that surface leaves a residue ( thats just bleached clean ) but if you run your hand across it the next day you'll find you get covered in dead algae - this is particularly true on cladded surfaces
after pressure washing we treat with Hypo - heavy black spot via a pump sprayer direct to the lichen of a light solution via x jet
so my pressure washing would last as long as your soft wash system but stay cleaner longer as I've removed mush of the algae first allowing the chem to work even better
its all a sales pitch and a manipulation of how things are done
Darran