You mean PCI-e. The difference is bandwidth. PCI-e has more of it meaning you can pump data down it faster. Some of the newer drives are hitting SATA 2 limitations. I wouldn't worry about it too much though.
You're comparing different products. You need to look at the manufacturer codes.
NewEgg: 4679.4
Prophecy: R4570
http://www.newegg.com/Product/Produc...82E16820167053
http://www.prophecy.co.za/intel-ssds...2-p-91060.html
If anyone reading this plans on going SSD, make sure you've got a solid backup strategy. I've been hearing way more failure stories than the MTTFs suggest should happen.