Missed that, good attention to detail. That would mean that the "6" speed would get slightly better fuel economy. I do not have a handy sticker to calculate against. That said, I doubt the Hemi will be able to show a 20% increase. That would be 6 Cylinder with the fuel shut off at idle.
I ordered the Hemi with the 8 speed as I think it best meets my needs. If I was worried about economy, I would buy a Tesla! (I just can't do a hybrid!)