I belive in many respects the A320/330/340/380 are laid out in the same way. They're designed to transfer easily from one to another, however they are instrinsigly different aircraft. As you'd expect the way the handle, the checklists, emergency proceedures are very different. The only two "different" aircraft that fall under the "same" rating are the 757/767. Although they have seperate type ratings flying the other aircraft only requires difference training and a sign off.