As has be stated since I made the post. To hit a rabbit on the head with a priest the head has to be free, no hands etc, as the head is free to move and you have a living animal being held down it is going to struggle and move. not conducive to hitting it sweetly and cleanly to effect a kill with one blow every time.
When you chin a rabbit if done correctly it will be dead instantaneously. To do this correctly is not difficult look at a skeleton of a rabbit and just below the skull on the last vertebrae on the neck you will see that two vertebrae are wider than the rest place your thumb a