Ok, all you DIY'ers....

[glatt]

I'm used to seeing rigid conduit tubing in commercial and exposed applications mostly. Inside a wall, romex is where it's at in residential. BX, the flexible spiral armored stuff, was in our unfinished exposed basement growing up and is inside walls in commercial buildings, which are built to higher standards.

Armored cable and conduit are better, but both are more expensive and take longer to install and require critical details to be taken care of otherwise the sharp metal can actually cut into the wires and defeat the whole point.

I use romex, the plastic stuff. It's good.