Advantages of WFP:
No damage to sills
No damage to lawns/flowerbeds with ladders
No fairy washing up liquid stains left on sills
No looking for water to fill up the bucket
No Frames cleaned every time
No wiping dry
No ladder knee
Make more money "lots more"
shall I go on.......
Advantages of trad:
NONE imo
I would not say that Trad has NO advantages :
WFP can only clean certain windows where trad can clean all, Also for simplisity trad wins hands down, then there is inside work
So yes WFP is excellent but Trad has got its good points