[Saber Cherry]

Ice devils have great stats and are poweful mages, in addition to being big and dirt-cheap. They're bigger, have way more HP, much higher (natural) protection, and better stats (in every category) than Bane Lords. They are alive and thus can use regeneration, and are immune to spells that kill undeads instantly. They can self-buff with quickness, if desired, and cast falling frost. They have an additional integrated weapon (tail). They are amphibious and can lead all 3 troop types, and one of them can summon frost demons.

Ice devils - like most SCs - are virtually immune to trample, by virtue of their high defense skill. They are utterly insane, considering you get them at level 5.

Average? No. I won't claim them to be the best, but they do have exceptionally high stats and some other nice features. They outclass Bane Lords by a large margin in every way... except that there are only 7 of them. Well, and they have encumbrance, which has to be designed around, but is made up for by their immunity to anti-undead spells.

Edit: In my experience, IDs perform much better in combat than ADs. Wraith Lords are immortal, which is nice, but outside of my own dominion, I think IDs are better.