From my experience flying, it is always better to hold your original plan until it no longer works before changing to something else. I have seen to many times that an earlier flight have some type of IROP and the next flight go out on time to the same destination, even before the earlier scheduled flight departs.
The look on peoples faces when this happens is pure anger and confusion, but things must move on. Some people might get lucky and if space is available they could be moved to that flight, but with load factors these days, that cannot accommodate everyone.