Is a louder IC cable a better cable?

This may sound like a weird question but, from what I've been reading about IC cables, they can't really add anything but they can "get in the way". Assuming that's the case, would the fact that one cable plays louder than another mean the quieter cable is "more in the way"?
I'm demoing 2 cables. one is an RCA and the other XLR, one used with a retail of close to $7K, one new retailing for $2.5K.
I know the common answer is "Go with what sounds better" but here's the hitch. If the idea that louder means there's less in the way, it would also seem to mean that you're hearing more of what's really there, and that's a truer sound, so if something doesn't sound right beyond that point you can look elsewhere in the system. At this point it is very difficult to navigate the cable market because I know for myself that I don't know how to make an educated decision. The "listen and choose" method is the best most of us can do for now but in a way it's ignorant and childish.
I think a good way to "test" cables would be to run let's say 100 frequencies between 20Hz-20kHz and see how "purely" the cable transferred each given frequency. Maybe this is how they design cables now, but the industry is so shrouded in hype and non-disclosure that it all is a bit of a mystery. Any isight will be appreciated.