Alloy wheels are aluminum (usually cast) and typically clear coated Regular wheels are steel and are either chromed or painted black with a hub cab installed
Very slightly, VERY slightly exotic wheel material will make your wheels lighter and improve performanceBut for everyday driving you would Never notice the differenceIts just esthetics , Alloy wheels look better.
Alloy wheels are lighter than plain steel rimsThey tend to be a bit better quality and the lighter weight means you're spending less power on spinning the wheels.
