The console vault allows one to discretely hide the gun in the safe, before getting out of the truck. If it is under the rear seat, one has to get out of the truck and then stow the gun in view. I think the console vault is the better option, whether or not there is a vault under the back seat.
One negative I see with the under the seat safe is that they do not appear to make a shorter one that will fit with a factory Ford subwoofer under the smaller seat.