Our primary concern was absolute maximum performance on huge numbers of tiny files (terabytes of video cut into single-frame TIFFs) for video processing while also having at least some protection against a single failed drive. We were on a shoestring budget, so we couldn't upgrade our network to use fiber, so a SAN wasn't really feasible at the speeds we needed (SSD's also didn't exist yet). You could be right, but I know that I chose the one with the fastest possible performance and made sure there was an audible alarm if a disk failed.