Or put another way, a 36AA is roughly the same as a 34A ... But lots of people find underwires uncomfortable and prefer to only wear wireless bras, which rely on wider bands and straps to do ...

So a bra in a size 36AA is the equivalent size of 34A, 32B, and 30C, which theoretically gives you some more sizes to choose from. The war of the wires comes down to comfort (and wireless is winning).