In Fallout 4, it is believed that your ability to sneak is dependent on your armor weight (with heavier armor being worse). However, armor pieces can be modified with the shadowed modification, which "Improves stealth in dark areas...".
Does this outweigh the negative effect of the armor weight?
Even if it does outweigh the armor weight and yields a net detectability decrease, this (supposedly) only works in dark areas. So then you would actually be better off wearing no armor at all when sneaking in well or medium-lit areas (no armor weight).
I guess it really boils down to which of the following is better for pure stealth:
- Shadowed armor with lightweight modification
- No armor
(The armor does of course offer some protection, but let's set that aside for now)