I put all round cables in my original build... they are actually pretty nice to work with and bundle/zip tie well. The cables themselves didn't last as long as I would have liked... I've had to replace them one by one, and eventually (just last week) pulled them all out and replaced them with new ribbon cables. I was getting SATA errors with one of my SSD's... originally I thought it was the drive, but as soon as I changed the cables out, everything is fine. For that reason I don't use round cables any longer... although I don't know why a round one would be any less reliable than a flat ribbon. Just my experience.