How to choose between Health or Armor Runes as a Support after seeing the enemy bot lane???

Armor worth more then health when you receive physical dmg. Mr worth more then health when you receive magic dmg. and Health worth more then both when you receive both evenly.

This is a lie because health and resistance are in multiplicative logic. So at some extent you're better to build both.

You might want to double check, but armor runes are a bit more gold efficient then health I think... this might also make you favor the armor.