This thread is really more about how good is the wagtail more than how does it compare to WFP...
But there are of course occasions when it is the quicker tool.
Perhaps a better heading would be "Which is best, Wagtail or standard squeegee?"
In use it can be used absolutely anywhere a normal squeegee can be used, even with the flipper it is way lighter than having a standard squeegee and applicator.
Like any tool you have to learn how to use it, once you are used to it you would not want to go back to squeegee and applicator, even allowing for the fact that more detailing is often required, it is still considerably faster.
You get used to using far less water too, so much so that if you have to use a standard applicator and squeegee it seems really messy.
On large windows, shop fronts and so on it is really quick, and on insides it really is the tool to choose.
As with any trad tool, the higher you work using poles then the less reliable your results become, and in n o way can you compare to WFP.
Ground floor, if you don't have to use a pointer, and you don't have to clean lots of opening lights and so on, then you could be as quick or quicker than WFP, even allowing for the fact you may have to do more detailing, and if you like to wipe the frames down anyway, then it won't slow you up one iota in comparison to using a standard applicator and squeegee.
It looks a cheap piece of tack...expensively priced!....but Would choose this tool over the standard squeegee any day of the week....as would my girlfrind who works with me, to begin with she hated it, but now always chooses to go the wagtail route when having to work with the trad tools.
Ian.