I'll go for Holy II, Banish IV, and Banishga III on WHM just for growth sake, because I'm tired of mobs casting them when I can't, and to have some more divine magic to toss out.
I don't really care for nuking as a concept on WHM though. I'd rather Ultima went to SCH, and implemented as Light element AOE Divine magic. How that compares to previous FFs is irrelevent imo. SCH has no native divine magic and generally subs RDM, so Ultima on SCH would be a great way to make use of the Divine magic boost in Light Arts. I also think SCH needs a powerful unique nuke, and I'd like to see the behavior of the spell dependent on parameters like weather. Giving Ultima to BLM seems redundant since they're getting Meteor, unless it works in a unique way or the element alignment difference would be significant.
For WHM, I don't really care about anything but Reviviscence.