Can only give you my experience as it is Mick, worked for 20 years using trad pole and backflip for upper windows and normal trad gear for lower, never had a complaint, ok I couldn't do the upper frames but nobody ever complained. Its worth thinking about, safe, cheaper by far than wfp, work in any weather etc. I know people will knock this but 20 years stands for itself, cut in the top edge and there are no runs.
However wanting to be a pro, bought an ro in the garage and 20 litre barrels, backpack and poles etc. worked out of an astra estate, probably slower than using the trad pole but better job with frames done.
Now got a 175 litre tank in the estate, use wfp for tops but in reality I need a van. Run out of water and the backpack takes around 4 mins to fill from the tank.
If I was starting out again I'd go trad pole, the customers like to see a squeegee.
low overheads on start uo and easy to do, later progress into wfp.
All the best mate.