Not only RAM, SSD is SATA III, but using a different form factor and a proprietary connector, a la Macbook Air. The new Air also changed the already proprietary connector from the 2011 models, rendering unusable the existing third party SSD upgrade options. Wondering if MacbookPro SSD connector are the same as the new Air's or not...
I'm still kind of scratching my head about the use of SATA given these custom connectors. It keeps driver development simple, but at a cost in performance.
Well, not only driver development but also controller development. SATA is a standard where you can go buy the standard components. The connector probably has the same data lanes as a SATA connector, just a different form factor. Most of the space saving come from not having an enclosure like harddrives do - something which only words with SSDs since they have no moving parts and are thus dust-resistant.
Most SSD <-> SATA interfaces are themselves essentially a bridge. You could instead directly wire in to the SSD's interface. It helps in a number of ways, as the SATA protocol was really not designed with SSD's in mind. Under the covers, SSD's are kind of this weird hybrid of RAM and storage devices.
