I will never argue the point that one can hear an audible difference. It is too subjective.
But, based on actual objective testing, better shielding can provide better cable performance/noise rejection. This is not an opinion. This is fact and if nibhaz would like to acutally do some research and read the test results, you would know that these are proven results in actual testing conducted by BJ that is readily available information on their website, and not an assumption.
Based purely on construction and materials used, BJ makes a better designed cable than Cobalt. Whether or not you can hear a difference really depends on the user and the circumstances surrounding the installation.
As pointed out, these differences are only in audio/video cables, and far less applicable to speaker cable. For the latter, just make sure it is of adequate diameter, insulated, and in wall rated if used in this manner.