Seems to me all of the above is relevant if you are building in the wiring, in which case you may as well use whatever cable will handle the load.

If (like me) your build has the cables unpluggagble via XLR sockets then my preference is to overbuild it to buggery in terms of cable so that they are mechanically robust.

Hence will be using 4-core SY cable, 0.5 mm^2 conductors, with OD of 7.3mm which is within the 8mm max for the XLR plugs:

Screening is a bit of a bonus. Current capacity is 7A per wire so should be an adequate safety margin on that front too :-)

Can't remember the cost but last time I got some from a local electrical wholesalers it was very reasonable. Anyway I figure my time is the most valuable part of any 'hobby' build so I'd rather just do it once and make it bombproof so as not to have to go back and fix it later... especially with fiddly stuff like cables, which in my experience tend to get a hard life anyway.