I have been cleaning windows for 4.5 years, never done trad, only ever wfp. I did intend learning myself to do trad, but it has just never seemed necessary, so I haven't bothered. From a safety point of view, I would say wfp all the way, no contest, but maybe im biased. Yes, as someone mentioned, you could, in theory, do yourself an injury with a large heavy pole, esp trying to get at a hard to reach window above a conservatory or extension where you may only be able to reach it with the pole at full stretch and a shallow angle. But I have a few like that, and although it can be very hard on the arms, I have never 'injured' myself. Once you have been using wfp for a while, if you prefer it, you can invest in a lightweight pole, which will reduce the strain. Access issues to awkward windows, like velux's can be got around with a gooseneck. I have looked at them a few times, but I have managed fine so far without one, so, again, I haven't bothered!.