Hi Dave_b, of course geometry, the purity of materials and the like all effect the cable- until you have a termination resistance value that is low enough to swamp that stuff out.
As audiophiles, we have been working with single-ended cables that use exotic geometries and materials for so long that it is hard to imagine that those techniques won't also serve balanced lines the same way. If you don't have a termination, that is true. But if you don't have a termination, you will be limited in how long the cable can be, and you will be subject to the various artifacts that those materials and geometries impose.
Mercury records use to record the Minneapolis Symphony at Northrup Auditorium on the UofM campus here in Minneapolis. They used their recording truck to do the recordings- it had the recorders built-in to the truck. They placed the mics at the optimum location in the hall, and ran the mic signal a good 200(!) feet to the truck, which was parked in back. You have to ask yourself: how did they get away with that in 1958 when no exotic cable industry existed, yet did it in such a way that no matter how you improve your own stereo, those LPs continue to sound better?
The answer: the balanced line standard really works; really eliminates cable artifact! But-0 you have to play with equipment that supports the standard to really get the significance of that fact.