yes, reflectivity and shape of the reflector are important, as restrike reduces lighting, and the life of some bulbs.
kitchen aluminum is not a good reflector...worse than gloss white paint. kitchen foil isn't meant to reflect light, but rather, heat, and thus if you magnified the surface you'd see its not smooth. aluminum foil is more of a diffuser than a reflector. mylar is the wiser choice, followed by a polished, specular aluminum reflector, like what AHsupply.com sells.