For the World Cup, any stadium in the US will find a way to put top-notch grass on the field.None of those college stadiums will be hosting a World Cup game, they're too far out of the way from major cities.
I think the finals will be in a stadium with natural grass rather than grass laid on top of turf. So, I'd put Chicago, Philadelphia, and San Francisco at the top. Though, as we saw with Copa America, it was hosted in New York. You don't put a world final in Dallas. New York or LA.