Not sure about the comparison but my GF's machine is SATA II and the drive works great in it. You're probably not going to see a massive real-world performance difference between SATA II and SATA III on these things.
We have good news! We're able to get this part of your order to you faster than we originally promised:
"SanDisk Extreme SSD 120GB GB SATA 6.0 Gb-s2.5-Inch Solid State Drive- SDSSDX-120G-G25" Previous estimated arrival date: May 07, 2012 - June 04, 2012 New estimated arrival date: April 18, 2012 - April 21, 2012"