Why I ALWAYS choose BX over Non-Metallic (NM) cable: A real-world example.
Sometimes individual conductors run inside conduit is the only option, but when I have a choice between NM cable and BX, I always choose BX as a residential wiring best practice. There are two main reasons:
1) BX shields electric fields. Many of my concerned clients have spent a lot of effort and money to shield against and reduce their exposure to electric fields. Some even go as far to turn off the circuits to their bedrooms when they sleep to reduce their exposure. If construction, remodels and renovations are done with BX, the electric field exposure is significantly reduced. The cost is greater, but for a 250-foot roll of BX, it is only about $30 more expensive than NM cable. So for a small job, the extra cost may only be $100 or so, and even for a large job the extra cost should not exceed $1,000.