JONATHAN!
in reply to a message by Emma Cummings
I absolutely loathe John as a full name.
Despite that, here is where I would choose a full name over the nn as a full name: With John, you are deciding that your son will be John (maybe Johnny) and that is that. With Jonathan, it opens up the choice that he be Jonathan if he wants (or has 3 other John's in his class), and with Jonathan, he can STILL be Jon/John or Johnny, or any other nn he/others think of.
Despite that, here is where I would choose a full name over the nn as a full name: With John, you are deciding that your son will be John (maybe Johnny) and that is that. With Jonathan, it opens up the choice that he be Jonathan if he wants (or has 3 other John's in his class), and with Jonathan, he can STILL be Jon/John or Johnny, or any other nn he/others think of.