I think Valor has a next cruise desk. Only 5 ships have the next cruise desk.
Its similar in the OBC you get, but you have to pay the full deposit to book, not just the $100, the cost of the Next cruise cert.
Another difference is the certs are good for 5 years, on Princess they are only good for 3 years.
Yet another difference is the certs cant be called in to book with. If you buy them to take home they have to be snail mailed certified mail into Miami. They are then applied to the final payment, the $100 you paid comes off that.
... but at least the OBC concept is about the same as on Princess or RCL. Im hoping Carnival fixes them so you can call the # in and dont have to mail the original certificate into their offices to be applied.