I tried both this weekend, on on each side of the car. The blue painter’s tape worked well, with little residue, and no dirt adhering to the leading edges. It did have a bit of a lift at one end. The black electrical tape looked better (black background magnetic label with white letters on a black car), stuck a bit better, but did have a line of dust on the leading edge, easily cleaned off. Since the car needs a bath anyways after the DE, either works.