[newconroer]

The speeds both frequency and timings are too close to make a difference. It's the same architecture.

What you want to look for is which one has the lowest starting (default voltage). I know that they both come with 1.65, but the question is, at 1333 what voltage would the 12800 kit need?

There might be some reviews out there on the modules, or at least their product family, to give you an idea of how well they scale with voltage.

The fact that the 12800 modules start with looser timings because of the increases frequency, is an obvious indication that they probably don't have much flexibility timings wise. With the 10666 kit, you're getting pretty much what you'd expect at 1333mhz. So, no negative surprises.

Though that could be entirely wrong. It could be the complete opposite. Maybe the 10666 kit cannot retain it's timings with even a slight frequency increase, where as the 12800 will tighten up, and retain it's 1600 speeds. It's just for $37 more, I don't see a point in stressing over the CL6, when it could be that the 12800 modules will run CL6.