By financial budget, do you mean budgetary ledger? It's very specific funcitonality, which should not be implemented without real need. As for commitment and payment budget, it's very simple: if your client has the same budget for commitment and for payment, then you should choose update profile for 'payment' budget only. But some clients would have different budget for commitment and payments, depending of their cash-flow and financial regulations. Imagine that a client can commit (make POs) for 1M in year X, but he has only 750K for this year for payments. In this case, both commitment and payment budget ledgers should be implemented.