For starters they are different styles of beers.

Light lagers have a much lighter mouthfeel almost watery. Also the mash is supplemented with corn or rice to keep the ABV high but calories down resulting in Light malt profile.

A regular lager like old English or Budweiser have less fermentable adjuncts like corn or rice and more true malted grains making it have more body and flavor.

For starters they are different styles of beers.

Light lagers have a much lighter mouthfeel almost watery. Cheap commercial versions supplement the mash with corn or rice to keep the ABV high but calories down resulting in Light malt profile.

A Regular Lager like Old English or Budweiser have less adjuncts like corn or rice and more true malted grains making it have more body and flavor.