Power Cables - Third Party or OEM

The thickest, most inflexible, and most phallic cables sound the best. Or whichever costs more or sounds better.. I can't remember it's been some time since I listened to a power cable. 

Doesn't matter. Until electrons become sentient, wire is wire. 

Electricity is indifferent wrt brand names so you don’t need to pay big money, unless you want to, of course.

What makes a good power cable?

• Stranded conductors that are adequately sized for the amperage (14 to 12 awg is typically suitable for front end components, and 12 to 10 awg for amplifiers, stay with the larger size for power conditioners feeding multiple components)
• Twisted pair or cross-connected twisted quad geometry to lower inductance and improve resistance to noise
• Ground wire of the same or larger size as the pos/neg conductors and connected at both ends (counter-spiraled outside of the conductors, and outside of the shielding)
• Shielding - either copper braid, or braid and foil connected at source end (see shielding links below)
• Connectors with solid grip and a high percent copper metallurgy (gold or rhodium plating for corrosion resistance if preferred, but not necessary)

If you don’t want to DIY from raw materials, several well-respected cable manufacturers sell bulk power cord cable that has most or all of the attributes listed above and that can function and sound excellent when constructed with good quality connectors (i.e., Furutech and others).

Links about shielding can be found here, here, and here.

It's not an engineering discussion, it's a marketing discussion. Of course an OEM will recommend their power cords and not the competition's. The oldest marketing pull is trying to convince consumers that using one brand's product (whether it's recipe ingredients or auto parts) is superior to mixing and matching. It works.