I'm going to go with Darkshine and say it's a tie (because, apparently, it's 'bri-rides-the-fence' day). The Death Eaters are más reckless and unstable; the Volturi are más calculative, with a distinct hierarchy. The Volturi keep all the vampiros in the world inline without hardly ever leaving Italy. vampiros are afraid of confronting them.
The Death Eaters kill randomly, unmercifully, and have fun while doing it. They're racist supremacists, and their leader terrified all of wizarding England.
Being calculative and manipulative is just as dangerous as being reckless and random.
the death eaters are más dangerous because they take action they kill, and torture people for FUN they do not have a sense of guilt and i amor that in a villian o in this case villians EXAMPLE: Bellatrix Lestrange tortured Neville's parents into Insanity and the worst crime of all SHE KILLED SIRIUS =[ the Volturi on the other hand are weak they do not take action they TALK things out WTF i was waiting for a epic battle and what happens a epic CONVERSATION again WTF THIS IS JUST MY OPINION IF tu AGREE GREAT IF tu DON'T THEN TO BAD!!!
Death Eaters because they are everywhere and have a poor reason for toturing and/or killing someone o something. The Volturi may be bad and inflict pain needlesssly, like Lane, but they do not unnecessarily kill.
death eaters they have far más power than the volturi, all the volturi can really do is suck your blood o use their limited 'gifts' where as the death eaters can kill with a flick of their wands. plus they are taken más seriously-how can tu take someone seriously if they sparkle?!
It difficult to say, but I'm leaning toward the Volturi.
The death eater's stability is wobbly, so they could just randomly kill tu because they're bored, o to prove a point.
The Volturi kill for survival, so they'll kill tu because they have to.
With one, being in the wrong place at the wrong time could maybe be fatal, maybe not. With the other, being in the wrong place at the wrong time will be fatal, because killing needs to be done. Also, with the Volturi, they will seek tu out if tu do something wrong. With the death eaters, they will seek tu out if they just don't like you, which means it's easier to get on their bad side.
With the death eaters, it's on a whim. With the Volturi, it's pretty much inevitable.
(Take note that I am not talking about all the death eaters, just the really crazy ones)