Is better to run RAM at a lower CAS (7) at 2T or at a higher CAS (9) at 1T?
 
Here are the particulars from the Corsair site:
Corsair Dominator - CMP16GX3M4X1600C7
Size:  16GB Kit (4 x 4GB)
Performance Profile: XMP
Tested Voltage: 1.5
SPD Voltage: 1.5
Speed Rating: PC3-16000 (2000MHz)
SPD Speed: 1333Mhz
Tested Speed: 1600Mhz
Tested Latency: 7-8-8-24
SPD Latency: 9-9-9-24
Command Rate: ?

The EVGA ELEET app say 9-9-9-24 at 1T. At this setting in auto, it will boot and run Prime 95 with no errors.
If I change it to 7-8-8-24 at 1T it will not boot.  2T boots and I can run Prime 95 with no errors.

Thanks for advance for your help.

<04-05-2012 9:28 pm edited for use of the proper name, "command rate" and not clock rate>

I'd say tighter timings, all I've ever used command rate for was stabilizing an overclock. I doubt in the grand scheme of things you'll notice a difference between them, as RAM latency is usually not an issue for performance applications.

Thanks, Yellow_fever.