Well, as is being discussed, the band size matters a lot when discussing cup sizes.

A 36DD is pretty large, a 28DD is not in absolute terms. But in terms of appearance, a true 28DD will look quite large on a small frame.

I would bet a lot of money that many folks would prefer to think of themselves as a 34B vs a 36A for both reasons - you might feel like you're more ideally proportioned with a smaller band size and you have a bigger cup size to boot.