[Alneyan]

The probability to get hit depends on damage resistance, not on component size. So reducing damage resistance makes a component less likely to be hit, while increasing its hitpoints increase the odds of the component being destroyed. So, for a 10% increase in cost (if memory serves), your weapons are less likely to be destroyed before the rest of your components. This is quite important with leaky armour around, as weapons have a damage resistance fairly close to the one offered by the armour components.

In the case of genuine armour components (with the armour ability), the opposite occurs. The weaker the component is, the more likely it is to be hit, so Armour III (40 hitpoints) is more likely to be destroyed than Scattering Armour III (150 hitpoints) in the vanilla game. But since most armours in Adamant do not have this ability, they follow the usual rule, and so you should try to make them much bigger than all your other components.