Quote - Last time I opened a Vicky object in UV-mapper the number of UV coordinates was identical to the number of vertices in the mesh. But I guess V4.1 is so sophisticated that she even has invisible UV-coordinates. But as I said, I hate mapping, so if V4.1 truly has MORE UV-coordinates despite of being lower resolution, I stand corrected.

It's not the number of coordinates. You are right about that.
Density means how much of the UV space each coordinate set (polygon) occupies. V4's UVs are more compact (less space wasted on the map). That means that a 2D texture of the same pixel resolution on V4 will retain more detail (and not pixellate as quickly) in 3d space than it would on V3.
V4's UVs have a lot less distortion (UV stretch) also.
It's much better mapping for hi-res needs.

Friends don't let friends use booleans.