Memory with higher Mhz or lower Cast latency?

Question

I'm planning to by memory for my motherboard Asus AT3IONT-I. The motherboard supports:

2 x DIMM, Max. 4 GB, DDR3 1066/800 Non-ECC,Un-buffered Memory Dual Channel memory architecture

Which of the memories bellow is fasted/best choice for this motherboard?

1. 4GB 1066MHz DDR3 Non-ECC CL7 DIMM (Kit of 2)
2. 4GB 1333MHz DDR3 Non-ECC CL9 DIMM (Kit of 2)

The cost for both memories are the same.

Answer 1

Of course 1st, 1066MGz.

You will lose advantage of the 2nd variant because your motherboard is not supporting it. They will work at 1066 MGz, also you will be able to set lower timings on them, but maybe not the CL7.