I gave the option of light and medium because of a couple different reasons.
Sometimes guys have an engine that may have some rod or crank wear but still within usable limits and don't want to replace the parts. A Light resize will regain compression but not put as much stress on the already worn parts. Another reason some guys like our light resize is the break in is shorter than a medium so some prefer that and will accept less longetivity for ease of break in.
Medium puts the engine to near new tightness so a full break in is required as well the engine components need to be in good shape as it is going through the tightness and break in all over again.
It just gives two options for customers needs/wants.