Hangman's Noose vs Uni Knot
The Uni Knot is a slip knot that is adjustable.

The Hangman's Noose is not typically considered adjustable.

The Hangman's Noose when the loop is under load is pulling on the top of the knot as well as conventionally on the bottom of the knot which is truly tightening the knot. They are typically only used with thicker ropes because otherwise you run a risk of pulling your knot out under pressure. Because they tighten down they can end up with a "permanent" loop larger than intended or may not be adjustable when load is removed.

The Uni Knot while the loop is under load is only exerting force on the line and bottom of the knot (more cinching the entire knot), so it puts load on the knot but doesn't really tightening it which also allows you to loosen or adjust it when the load is removed. Because of the complexity of tightening/securing the knot, this is typically used only on thinner lines and is a typical favorite among fishermen for attaching hooks and lures as fishing line is thin and has little friction. On line that can be stretched, loads on the loop and line can seemingly tighten the knot since the line is thinner(stretched) under load and make in not easily adjustable when load is removed; I say seemingly because the knot isn't considered tighter when load is reapplied.