The differenmce is that the BA Blue and BA Premium Plus are botrh BA cards. The rules state that you can only have one or the other and tranferring betweent he two is very simple. Amex Gold is a totally differenet card with no connection to BA (other than you have the ability to exchange Amex points to Avious points). The same goes for any other non-BA Amexs, they are different cards which require the full application process to be completed and will not automatically close any other cards.