User blog comment:Mathmagician/Why Dart Traps?/@comment-4594221-20120109005832/@comment-4674838-20120109011303

Flat surface. Lava pit in the center 7 blocks deep (monsters that fall in can't get out) and say 6 to 20 blocks wide (you can fiddle with the width to match your preference). Stand underneath it. All monsters fall into the pit to get to you, and the lava will kill them faster than dart traps will. Hell, you can even add dart traps along the sides of the pit if you really want to.

Dart traps don't have some mystical inherent property that makes it so that you have to walk less to pick up drops. Lava can do the same thing if you just build your farm properly.