I would probably go with what works for most of the type of schools the kid would apply to. I already have a strong sense of what type of student each of my kids is. They range from could get into Top 20 (not saying would, just that the raw material is there and it would be a good fit) to hoping gets into our state flagship and the bottom of the meet full need privates.) However there does not seem to be a good way to determine how they treat 529 plans in the abstract. Very frustrating.
In any case I am seeing huge differences in general, outside of this topic, even within the same category the more I play with the NPCs. The differences between Harvard and Brown are striking for example. I would pay 50% more at Brown!