Passenger trains need to operate at higher HP/ton. A WAP7 hauled 24 coach train barely operates at 4 HP/ton, and the tractive effort is not really sufficient to comfortably haul longer rakes at consistent speeds. It will always be better to have locos with the highest HP possible within the axle load limits we have.
But personally, I would have vouched more for a high-HP loco or a next-gen passenger loco based on the WAP5, instead of the WAP7.