If your action's low at the middle of the neck, I doubt the neck is curving. Put a straight edge along the neck between and parallel to the strings, that'll tell you to a degree. Again, check the neck shape ("C" vs "D" shapes, say). Is one neck thicker than the other? Measure the width of each nut and compare. Are both fingerboards dead flat or does one have a slight curve edge to edge (which is a feature, not a bad thing). Are the frets taller on one fingerboard than the other? You can see that pretty easily. And yes, measure scale, edge of nut to saddle.
2015 Connor spruce/Indian rosewood
1978 Ramirez 1a cedar