3Gbit SATA is not that bad for regular spinning disks. For SSD it matters greatly though as one channels get capped with an SSD on 3Gbit. Recently bought an Corsair Force GT 240GB for a laptop and it R/W over 500MB/s so 6Gbit was necessary so that it would not get capped. But the fastest spinning discs put out about 150MB/s so they are not even close.

DSP8000SE, DSP7200SEHC, DSP5200SE sides, DSP7200SE rears, 861v8, 210, Sim2 Ultranero 4, Stewart Cinecurve 2.35:1, XEIT CM-5E Anamorphic lens, Dune HD Duo Cinema 8K and Wireworld Platinum 48G HDMI -> UHD722 -> Shunyata Omega Ethernet. Shunyata/Furutech power-cables/filters. SR Master Fuse@861v8. Uptone Etherregen with 10MHz OCXO clock.