Solid core OFC vs stranded OCC copper

Certain patented cable designs favour stranded cables ( eg CARDAS)

Both the Clear and Cross lines feature Golden Ratio scaled, ultra-pure copper multi-stranded Litz conductors, carefully chosen dielectric materials, and innovative manufacturing techniques.Cardas litz conductors use ultra-pure copper, in a Golden Ratio scaled, multi-stranded arrangement. Each individual strand is coated in an insulating enamel.

Litz conductors must be tinned before they can be soldered to a circuit board or a connector. At Cardas Audio, we remove the outer jacket with hot tweezers, dip the wire in Cardas Rosin Flux Soldering Paste, and then hold it in a solder pot for several seconds, until the end is tinned.

The Clear line refines the design principles found in Cross, with new discoveries in metallurgy and termination techniques. Clear cables have Matched Propagation conductors, in which the propagation rate of the conductor is matched to that of the dielectric, as described in George’s latest US Patent, #7,674,973.

Litz wire is a particular type of multistrand wire or cable used in electronics. The wire is designed to reduce the skin effect and proximity effect losses in conductors used at frequencies up to about 1 MHz.  It consists of many thin wire strands, individually insulated and twisted or woven together, following one of several carefully prescribed patterns

I'm with @jaymark .

Solid core OCC in Teflon.