Of those I have tried, my favorites are made from multiple strands of individually insulated, relatively small gauge (i.e., 20-24 awg), solid core wires.

I've been using 14 gauge UP-OCC solid core copper in Teflon for years. Recently, I've been using loose-sleeved 18 gauge solid core silver and find it faster and cleaner with a more neutral sound. 

Multiple stranded (MS) cables sound more detailed, deep, and focused (smaller sound images) with less sound stage and less bass. So, it is good for string and brass instruments and acoustics/classical music. Generally, MS sound makes feeling bright, excited, and happy.

Solid-core cables sound punch, more energy, and big/thick sound images and stage (the wall of sound) with more bass. SC cables are good for percussion instruments and Rock/fusion music. Generally, SC sound makes felling sad, and down.

We, cable designers, mix wires to make balanced sounding cables (and to sound close to the original music). To make a good cable, we need the best reference audio system to hear cables. A problem is all their audio systems sound veil and un-natural. The veil sound means the signal is broken and distorted and those systems can’t be a reference system. Sadly every audio systems in the world are sounding veiled and un-natural. In the land of blind, the one-eyed man is king. I only know what they are doing wrong. Alex/wavetouch

Check out Magnan speaker cables. This company has came out with a concept of multiple wires smaller than a human hair, in a flat-shaped cable. They sound pretty amazing and extremly neutral. For those looking for solid copper speaker cable I would recommend WhyNot speaker cables which are probably the best on the market. Both concepts have advantages and inconveniences and system matching is always an issue. To solve your dilemma, you should test both in your system and decide which one to keep. 

Duelund DCA16GA tinned copper multistrand wire in cotton and oil