It is true that a 12 AWG is a 12-AWG wire before insulation is added. The 12 AWG of bare copper will carry the same current, regardless of whether it is a solid copper strand or multiple copper strands.
It can be made more flexible or less flexible depending on its application. This can make certain applications more beneficial.There are different colors available in 12 AWG sizes. Visit baboombaboom.com/12-gauge for best quality wires.
You could build a harness with the stiffer electrical wire you use to run through conduit and walls. This would make it more difficult to solder, crimp, and terminate.
PVC wire is very versatile. A 12 AWG standard PVC wire has 65 and a 12 AWG standard electrical wire has 19 strands.
Installers who use less flexible copper wire get the same benefits. Installing a stiff wire won't cause it to lose its shape or become twisted. PVC wire pushed through conduit will not work.
Another advantage of 12 AWG electrical wire is its ability to be used outdoors in conditions that PVC wire can't. It's used in so many places, including in conduits, that engineers have discovered that it will be exposed to all kinds of chemicals and gases. The insulation must resist these substances to survive.
Keep in mind that copper 12 AWG will always carry the same current, but insulation determines where and how the wire can be used.