I think the battle will largely be in the Gap - we'll get the maudlin pre-Helm's Deep scene of the weary soldiers (and other able-bodied conscripted civilians) riding off to die, then we get the reaction shot of Agelmar on his balcony with jaw dropped watchingSpoilerRand go Super Saiyan with the Eye in the distance, then we get the triumphant humanity riding back after the nuke.
Besides, if the fighting is away from the walls, Rand will really be able to cut loose and give us a preview of what is to come
Sidenote: I'm unsure if this is the case but if we start getting newcomers to the series in here we may have to start using spoiler tags even for EotW and NS stuff.