Only reason to takeout at diamond is uncontrollable time constraints. If you can at all get the extra few days, go to pearce. The helos and tourists will help break you back into society so that the culture shock in vegas doesn't give you a heart attack.
Pearce while mead is low for sure. Diamond is too abrupt an end to the dream. Diamond to Pearce is 16 hrs at flow in the mid teens. Plus, the canyon below diamond is spectacular. Some nice splashies too.