After Effects and Photoshop CS6 take .Looks via the LUT engine. That indeed allows for using primaries with low mid high differentiation and should yield really good results.
Secondaries can be expressed in a LUT as well, but I would typically not recommend using them when you want to integrate .Looks with your After Effects workflow. Here's why:
- a LUT is never as precise as you'd want it to be for something as complex as secondary color grading - a LUT is always based on interpolation (as opposed to applying the effect in SpeedGrade - there it's all native, no interpolation at all)
- For a good key you would typically use the denoise and the blur function in the secondaries. Both (by nature) don't translate at all into a LUT, so you'd have to give up using these 2 important tools
- For a lot of work you'd want the LUT to be accompanied by a mask. That's something that also can't be described in a LUT.
Think of the LUT support for .Looks you created in SpeedGrade more as a really helpful tool for matching your comps to an overall look you design, not necessarily as the tool to apply a final grade.
Hope this is helpful.