A comparison between ours (milled) and a cast selector.
http://i75.photobucket.com/albums/i3...roovecomps.jpg
The contact area is much greater on ours, it also has tall shoulders to prevent the selector from being backed out when it's rotated out of the detent holes. The cast selector's shoulders are so shallow, if you rotate the selector to 45 degrees you can push the selector out, there are folks out there that do use this method to remove the selector.
That it can feel rough isn't just the detent's job, it has to do with the detent groove on the selector as well.