I would say YES. With aluminum being brigher or having a greater reflectivity percentage.
While white will reflect all the colors of light back at your eye there is to some degree a percentage of light that gets absorbed or diverted at the wrong angle to be benifical.
With a polished aluminum reflector the surface is going to be much smoother than white plastic thus you will get beter control of where the light is reflected. Plus I have to belive the metal will reflect more of the light than a plain white surface.