User blog comment:MilitaryBrat/Lord Voldemort vs Darth Vader/@comment-422690-20111217205456

Vader wins. The Force doesn't require a wand, and things like force grab and force choke are cast on-target, meaning no travel time for a shield to intercept. On the other hand, spells have been known to be blocked by physical matter (see any fight scene later in the books), and guess what - a lightaber is made of plasma, which is a state of matter, not energy as is commonly believed. So, we've determined that Vader can block Moldy Voldy's spells, while Voldy can't block Vader's force usage. Besides, the books state that after he dies physically, it takes a long time for him to recover full strength. So, should Vader kill him and not Nagini, Voldy will be an corporeal spirit - almost analogous to a force ghost, except he's solid - that can be dispatched easily.

As a counter to the supposed "Stormtrooper effect" is basic battlefield psychology. The stormtroopers aren't seeing a faceless opponent in Luke, Lei, etc. They're seeing people. Now, it's been previously confirmed in the movies that Death Eaters operate in masks, thus dehumanizing them and killing the stormtrooper effect. The might suffer it with Voldy, but Vader can take care of him easy.