Which is better KingStone bus 1600 or 1800?

I'm getting a new machine and I don't know which one should I get

Kingston 2GB DDR3 bus 1800 MHz CL9
or
Kingston 2GB DDR3 bus 1600 MHz CL9
or
Kingston 2GB DDR3 bus 1333 MHz CL9

I mainly use vmware and I wonder if having faster RAMs better than having alot of RAM. for example, 4 GBs of bus 1800 is better for example 8 GBs DDR2 bus 800?????