In the general case I've found Mind Hunt to be a more effective spell. Easier to cast, costs a little less. But, as discussed above, there are some commanders who are particularly vulnerable to this spell. Additionally, Vengence of the Dead is targetted and thus will ignore all the chaff scouts that might be accompanying your intended target, unlike Mind Hunt or Earth Attack.
edit: Oh yeah. You cant get feebleminded casting Vengence of the Dead, either
