The rigidity of the wheel takes more precedence over weight. We're talking at most 2lbs extra for some wheels. Decreasing weight while maintaining strength/rigidity means wheels will cost more just to spend more effort finding every method to shed weight without reducing that epic quality we all seek. Good wheels means more R&D and effort to optimize these factors (Volks & BBS).
Under cornering loads, a stronger wheel (usually slightly heavier) is faster than a lighter wheel. We also see a lot less bent wheels from track and street use using those "heavier" wheels. Of course, this is from an actual use and abuse perspective.
