Which RAM package for my Toshiba R700?

I have a Toshiba R700 notebook (core i7-m620) with 4gb of RM installed and I want to upgrade to 8.

I don't know whether I should get pc3-8500 @cas7 or pc3-10600 @cas9.

Here are the two packages I'm considering - which should I get for best business applications performance?

8GB Kit (4GBx2), 204-pin SODIMM, DDR3 PC3-10600 upgrades for Toshiba Portege R700-S1311 Laptop/Notebook, CT1441009 from Crucial.com

8GB Kit (4GBx2), 204-pin SODIMM, DDR3 PC3-8500 upgrades for Toshiba Portege R700-S1311 Laptop/Notebook, CT1441017 from Crucial.com

thanks