Difference between holy and light damage?

Monk smiting spells deal holy damage.
Monk smiting staffs/rods deal light damage.

Are these two names for the same thing or is there a difference? Im thinking in terms of effect on undead creatures and ignoring armor here.

Yes, there is a difference. Light damage is useless.

Light dmg is elemental dmg. Air magic spells do light dmg. And armor vs elemental attacks protects you from light dmg. Holy dmg is isnt elemental dmg. Only your armor vs everything protects you vs that. And it is greatly superior.

Its light damage not lightNING... You can always test it

The effect on undead creatures is the same; however, you are correct on the armor ignoring part.

Through my own tests with holy and light damage, they seem to do the exact same thing. Don't ask me why they're named differently.

Let me give a counter-example:

Necro spells often do Shadow damage.
Necro wands/staves do Dark damage.

They seem to be the same though. Correct me if I'm wrong.

Oh yes, my mistake. Then i guess light dmg is the same with holy.

The difference is with the armor resistance. Weapons with that type of damage still call enemy AL into the formula, while spells do not.