It would of course depend on the solution they go for, but if for example they used a cryptocurrency like Bitcoin, the difference would be that the 'int' in you

It would of course depend on the solution they go for, but if for example they used a cryptocurrency like Bitcoin, the difference would be that the 'int' in your account right now is forgable -- i.e. the bank can go in and just adjust it up/down as they see fit, with only regulations (i.e. messy human decisions) to stop them. A CBDC backed by a proof-of-work scheme is unforgable, meaning said currency could be transferred between multiple banks (even potentially abroad) without having to worry about whether said bank obeyed all the regulations correctly or not.