Awful. Voldy is WAY mais evil than aro!!!! I shall elaborate. Aro is a power-hungry vamp whose power comes solely from his guard. He relies too heavily on Jane and would not punish her. He's just a peace-keeper who wants to be strongest. Voldy is a well-built, evil character who lead his comensais da morte properly. They could not do without him, but he could do without them.
Terrible. The death eaters would not have a strong leader, and therefore- would not BE strong. They would have no chance at accompleshing what they ha in the past (e.g. Killing muggles, taking over the ministry, killing Dumbledore or any other wizard, ect.) That, and poor Bellatrix would have no one to obsess over! X)