I have two pages myaccount.xhtml and selectbank.xhtml In my account page there is one option for recharge account in which user will enter the amount when user will press su
Your use case is not of simple request/response cycle, the life span is more than one request response which makes it candidate for session scope.
Using hidden variable or GET parameters in URL is not good practice especially for a banking application. Where security is so important dont compromise on small memory foot print.
If flash scope map simplifies the case you can use it, but I would not go for such a thing.
Update: Forgot to mention you can check Conversation scope too.