>>36177179Mannfred is to control the magic phase, but he does so by killing. Unless you can get him against something squishy, he's not that great. Fantastic horde-deterrent though.
He basically deals a lot of attacks, and generates Power Dice by doing so. GREAT if you can use him well against anything like Skaven, O&G, other Undead armies, and so forth, but pretty shit against elite armies like Warriors and Ogres.
Neferata cripples the shit out of anything she stabs with her magic dagger, and is the best of the mounted Mortarchs in melee. Weakest magic, although using her to blast and curse deals more damage than the others regardless. So you use her to absolutely fuck the shit out of armies that rely on characters, like other Undead or Empire.
Arkhan is Nagash, but cheaper and less effective.
Vlad is classic Vlad, being a fucking awesome durable vampire. Stick him in a unit of whatever.
Krell is killy as fuck, and cheap. Stick him with Grave Guard units, as big as possible.
Out of them all; Vlad, Neferata, and Krell are the most useful in my evaluation. I prefer Nef because there's nothing like making a character useless like her, and she's still a good caster. Vlad is all around useful, Krell is only good for the GG combo really but he's damn good at it.
Looking at what you're working with, all three would be good. I'd suggest Arkhan, but you may want a different playstyle in your cheaper character for variation.