on OEM lighting you see some cars with farily small headlamps, and some with HUGE things with big reflectors.

My question(above)

now we live in a not so perfect world, so this is what I'm comming up with....

Yes, because if a bug splats your headlamp lens, on a larger reflector it would affect the beam less than a smaller relector(like a Projector)

and a Reflector Defect would cause a smaller reflector beam patteren to change more because it has to project a more concentrated Light with greater projection than a larger reflector.

Did I sastifactory answer my question, and if I'm wrong how can a smaller surface area reflector be more effeiceint than a Larger reflector?

All other things being equal, the larger the reflector surface area, the greater the number of images of the light source that would be captured & reflected. A bug splat of a given size would affect the end output of a small projector more than that of a large reflector, but if you drove thru a 'bug storm', the large reflector lens would pick up more bugs faster than the projector lens, due to the difference in frontal areas.
If the headlight "stylists" (what a world we live in) and marketing people could have their way and somehow bend the laws of optics to their wills, there would be cars out there that had legal (minimum) night lighting, and NO visible night driving light-producing source showing on the vehicle at all. This concept was actually tried back in the 1970s & 1980s with 'hideaway headlights' that were only visible when the headlights were on. Headlights ugly, sheet metal pretty, uhhh!!!