I recon I can do it twice as fast with a scoop than you can with a vac, but that's just me.
With the vac you need mains power from a Genny or the customers house, more expence for the Genny, or if using the customers power they have to be home, then you need a 110v vac and a transformer to abide by H&S if you use 240v then it has to be with a RCD.
Gutter scoop, just screw on the end of your pole and away you go, no need for custy to be home and can be done in the rain.