My experience has been that the signal from your cartridge is especially susceptible to EMI. I had a phono cable from a very well known company and everytime I tried to use my TT there was background noise from a radio station. I switched to another cable and the problem went away.
So, I would say that there are two things that make a phono cable different from a regular IC. It needs better sheilding and many arms require a din plug. Other than that I would say that the differences in the different brands are the same as the differences in any IC. Which means some people will claim that changing from one to another is as significant as buying another pair of speakers and some will say that it will have about the same effect on your audio system as painting your walls a different color.
So, I would say that there are two things that make a phono cable different from a regular IC. It needs better sheilding and many arms require a din plug. Other than that I would say that the differences in the different brands are the same as the differences in any IC. Which means some people will claim that changing from one to another is as significant as buying another pair of speakers and some will say that it will have about the same effect on your audio system as painting your walls a different color.