Selection outlines go through everything, so if you have engineering data, So many times, they don't really illustrate what you have selected.
I'd LOVE an option to turn on that slightly shades the visible parts of what you have selected.
This is a setting I Always change in Rhino. The default is wireframe selection. In the view settings you can change it to shade selected. So if there are objects in Front of your selection, you don't see your selected object.
This is Fantastic for figuring out what things are visible for renders, and leaving all that internal stuff behind.
The outline still has some value also though.