I was trad for 9 years before wfp and have now been wfp for 3 years.
Disadvantages are basically the change over from trad to wfp, customers in general don't like change so you shed a few. It's also very hard to get good results on the first clean especially for a wfp newby. Lots give up wfp in the first 3 months for this very reason, the body also needs to adjust. Another disadvantage is the cost of equipment, gone are the days of spending no more than a few hundred on gear each year, it's more likely to be thousands. And as time passes you realise that it's worth buying the more expensive stuff, like carbon poles.
Advantages, people in the long run prefer wfp to trad, they realise it does a complete job with no risk. You can get through much more work, about 40% more at least. New customers like it as well, your much more likely to pick up new customers wfp than trad, just the fact that your seen more with hoses running all over the place.
As for freezing pipes and tangled hoses, these are things that are eliminated with a good working method. I've only taken 1 day off this winter due to snow and that was because I didn't know if the roads would be clear. I've had overnight temperatures down to -7ish but have heated the water before work and also keep in mind not to leave the hoses or poles out in the cold doing nothing.
I think nowadays that a professional wc needs both tools in the bag trad and wfp, especially for commercial.
Simon.