oh, I am not saying to worry about it at all. The issue is minimal at best and unless you have some sort of measuring device on it you should notice no diff. I have round in two of my systems and have no issues. (one for the last 3 years also)
scsi is serial i believe and like sata, a serial connection is asynchronos which eliminates the xtalk issue. (no clock to sych to and so no parallelization of any given sig) pata is not, and that is the problem. The shielding is more for outside interference, and only does minimal on stopping internal interf. (as far as I know anyway) That is just the fundamental issue of synch parallel signal transfer that the original layout of the flat cabling dealt with. Each wire was only adjacent to at most 2 instead of the multiples in a round wire. That is why the cable is flat, otherwise it would have been round from the start. That is why scsi is round.
I actually think that round is cheaper in most cases that flat to make (at least in all other wire configs it is...) they charge more for round just because they have been the fad the last few years and we will pay it.
Modders were making them "round" back in the day (fancy razor work) knowing that the minimal xtalk there was could be handled with the faster systems comming out and so did it anyway. (any corrupted sig must be re-tranfered) Again, this issue is so minimal with the modern cables and equip that you should get any cabling you want and enjoy how it looks.