Full loom of the same cable brand vs mixing and matching.

it will likely depend on your system.
 

For most of my 50 years pursuing the high end I was forced to choose the very best components and therefore needed to choose cable and interconnect specifically for each connection. But over time a few companies began offering best of class / sound family components for DAC, Phono Stage, preamp, and amp. In this case it is preferable to ID the ideal cable / interconnect and use all the same. So, for me all my components are Audio Research and they are highly complemented with Transparent wires. So that is what I use except for the power amplifier power cord, where I use Audio Quest Hurricane… a great cord… but at the time I did not want to spend $6.5 K on the Transparent Opus and the Hurricane was better than the Transparent Reference level.

So, do you have a mixed brand system or single brand? 

I wound up with a full loom of Acoustic Zen cables just because every time I added another the sound kept getting better.  That said, I’m firmly in the “whatever works best” camp and if something comes around that sounds better I wouldn’t hesitate to change.

I prefer a variety of fruit in my loom. 

I asked the same question a while back as my dealer was insisting that my mix of cables would not sound as good as his very expensive loom of cables. The consensus I received was the quality was the same is important and that the same manufacturer was not necessarily better. 
saved me thousands.