sminlal's answer is a really good one. It's very true that sequential write speed doesn't matter so much in the grand scheme of things these days.
The only time you're likely to notice it is when you are copying very large files from one SATA drive to another on the same system. For normal use it will never be an issue. You'll never hit that limit when ripping DVDs or bluray, downloading with bittorrent etc or even copying from a USB device. Access time (specifically, average write latency) is going to matter much more.