CA, Vignetting, Distortion--- Questions?
Although all three lens issues can be corrected in photoshop (ACR), which one is most problematic? Which one degrade photo quality more?
Too general a question, as others have noted. Speaking really generally, I would say that vignetting is the easiest to fix; followed by lens distortion. CA can be difficult or impossible to fix depending on the location, type, and severity of the effect.