It depends what kind of charcoal you are using too. My guess would be they will use the same amount of charcoal becuase refueling isn't probably going to happen. Instead, you need a certain amount of charcoal to be lit to have a certain temperature to cook at.
Say for example, you use Kingsford. Those stay lit and put out a steady temp for a couple hours. Both of those items will be done within that time, so the same amount of charcoal is needed to cook them, and then you will have extra fuel for a while that simply burns up. Royal Oak lump tends to put out good heat for only about 45 minutes from my experience. Even so, I would imagine both the chop and the porterhouse will be done in that amount of time, so same amount of fuel is still needed to reach the temp you want to cook at.
Hope this helps.