Not sure on that one to be honest Mike.
Both methods have their risks, ie trad - danger of falling off ladder; WFP - someone could trip over the hose. Risk assessments would be required in either case.
As I said, I am trad, and although I am far from fallible, I am very, very careful and risk assess every time I move the ladder. I have had several falls in the past, fortunately in each case without the need to seek medical attention. This is why I now constantly risk assess.
I therefore fully appreciate that ladders can be dangerous, but only as dangerous as the person using it. If I had a fall from mine and I got hurt, I would take full responsibility, as no one has forced me to climb it.
If I went WFP, and lost control of the pole and it clonked a passer-by on the head, would this make this method safer to use? In my case, it would probably not. I am built like Hercules before the sand was kicked in his face, so I would probably not have the physical strength to operate a WFP set-up. I can handle a ladder and bucket OK, so I will stick with that and accept full responsibility for whatever damage I cause using trad methods.

John.