Just for reference, the "U-Haul" pan does not have increased fluid capacity...it's identical the the stock pan with the addition of the drain plug.
I was going to say that but I wasn't 100% sure. From what I remember, the reason the u-haul pan exists is because u-haul wanted to be able to easily service their vans. They have enough pull with Ford (and GM) thru their fleet accounts and large numbers of vehicles ordered that Ford complied with that request by simply modifying the standard pan and adding a drain plug. Probably costs Ford very little to do that and if it keeps a large national fleet company happy, it only makes sense for them to do so.