As was discussed in question Is armor's DR additive and covering whole body?, the armor rating seems to be total, not for each body part separately.
Supposing that's correct, what exactly does 'reduces limb damage' effect in Strengthened armor mod do? Reduce incoming damage to a limb for some percentage? Is a piece with this mod better than a piece with a higher armor rating but without such mod?
Best Answer
Limbs have their own health bars, independent of player health. When these are depleted (by taking direct hits to the limb in question), you'll be crippled (Indicated by a wounded pip boy icon popping up in the top right of the screen momentarily).
When one of your legs is crippled, for example, you'll find your movement speed severely reduced.
Using a stimpack will heal any crippled limbs, in addition to healing player health.
The Strengthened Armor mod, and other effects that increase or reduce 'limb damage' serve to prevent you from being crippled as easily.