I've been lately into darker images (or at least true to the original, if the original was dark). I'm wondering what the best practice is for exposing for the highest quality end product.

Let's take a hypothetical example. Say I underexpose in camera, so the information is all in the darker end of the histogram, but no clipping occurs. Alternatively, I could overexpose, where all the info is in the lighter end of the histogram, but still no clipping. If I'm going to correct the exposure in post (eg, make the darker picture lighter, or the lighter picture darker, to achieve the same exposure), are the quality of the pixels going to be better in one scenario or the other? Are all pixels equal, and equally usable, if they lie within the boundaries of the histogram?