In the one image bottom, we have a SWAT (or other armed forces) with a MATTE black M4,
low reflectivity= IDEAL TACTICAL
The "fighting tool for those who know".
In the other image at top, we have a very pretty M4 with reflective surfaces undesirable for field USE
Its perfect for showing others, and posting pictures of.
Such mods are boasted of their weather / anti-rust properties (rather than keeping their gun oiled and cleaned as anyone ought to do).
i.e. the boasting rights of a Keyboard-Jockey.
This is the same reason a $4000 1911 is said of "what you show your friends"........and a Glock is said "what you show your enemies".
Here ended the lesson.