No real difference - you're allowed to withdraw as much as you want as Pro, and the fee is 0.5% of the amount over $5,000

To me it's the interface.
DDA format is simpler - you type in the amount you want to withdraw, you're told the fee, and if you're OK with it the sum of the two are withdrawn. If the sum is less than your balance your application is rejected and you have to lower your withdrawal.

FPS is confusing. You type in a proposed withdrawal amount and you are told the fee on that proposed amount. But if you're account doesn't have that much money the transaction goes ahead anyway - the fee is the amount you agreed to, but the amount you proposed to withdraw will be adjusted to the amount you actually have left after deduction of the fee. So in order not to incur excessive fees you have to do a manual check to make sure the sum does not exceed your balance.