To highlight the difference a bit better than I have in previous posts, here are two pictures:

Beret:


Balmoral:


The Balmoral doesn't sit quite as tightly on the head and seems (usually) to be both heavier and broader than the average beret. The Balmoral also has a broader band (sometimes diced), while the beret's headband is usually very narrow (i.e., the "floppy part" begins right at the narrow band, while the same part of a balmoral starts a bit higher up).

Of course, it is your decision to make - if you feel the berets available are similar enough to a true balmoral bonnet, then go for it.