Rules Update: Restraining Items, Quickbind

If that is true, then the only difference is time of creation, and build cost to create.  In which case, leather restraints still seem superfluous, given that manacles are permanent, and leather restraints are one time use.  I'm just not seeing why someone would create them.

Easier physreps to carry? Cheap way to bind people?

If the manacles have a locking mechanism, is it harder to escape from them?

Leather Restraints cost less time and CP, and therefore less money to make - 5sp vs 10sp / 1 Gold.  At higher levels, it's not a big difference, but for beginning characters, that can be a lot, for both the crafting Smith to make them, and the purchasing character.