Often when I take a high ISO (relative) I find myself also adding an extra layer of edit ("remove noise") which I think just hurts the image. Adjusting exposure alone I feel does less damage.
I really don't find adding exposure on post (when RAW) damages as much as adding ISO and adding noise.
ISO is really just boosting a sensor sensitivity to light which I feel is not optimal and adds it's own set of artifacts. I would always prefer to add more exposure and me being the one adding the artifacts and playing with the edits, rather than the camera.
But then again, I just shoot for hobby and not a PRO! You can check out some of my pics at @franciscojgo
Now if i’m shooting indoors and my glass doesn’t have a decent f-stop that shoots in lowlight, i can leave my aperture down and raise my ISO to maybe 1200, but when you do this, that is when you’ll get grainy pictures because you’re moving away from the cameras sensor base ISO that it’s calibrated for.
But if you want to adjust everything in post processing, you’ll need to shoot RAW because JPEG do not hold enough data that’ll allow you to adjust it accurately.