I don’t understand. Is there any difference between inset and extrude ?
I mean in the case I want to reduce thickness : I can either do it with inset or extrude the faces, leave it in place and scale.
Using the Depth option with inset seems fairly similar to me to extrude and scale.
So the question is: what is the difference between inset and extrude+scale. Inset tries to offset the edges with the set amount, while scaling doesn’t because the selected geometry from the extrusion is scaled along the set pivot point (median by default).
You won’t notice a difference with a plane or with a side of a cube, but try it with U shape mesh and it starts to make sense.