Treasury allows you to place a blasting charge, blow up the vault and take a vast amount of gold bars which can be sold at Gold Buyers in Kavala and Old UNMC territory.
RBA International Reserve contains money bags, where once you have broken through using a code breaker you can take these money bags and change them into cash at the Laundering site.
Main difference is that Treasury can give you a lot more cash of successfuly done, however it is generally considered harder to do.