If JeffB were here, I'm positive he'd chime in something like this-

Specs, and their rank of importance-

1- SPINE. Spine must match as close as possible in order to get repeatable accuracy.

2- Weight.

3- Straightness.

If you can only have 2 out of the 3, I'll take the best of 1 and 2 with the worst of 3 any day over any other 2 out of 3 variation...

Unpredictable spine degradation seems to be the big knock on most current carbon offerings, not straightness.