Great question, and honestly can't answer that for certain because I didn't want to double book on the same flight to check the MTM price, but I am almost certain that the new flight was more certs because: (1) it cost more certs when I originally booked, (2) the cash price for mint when I rebooked was nearly $2k, and (3) there was no change to the points price, which seems to suggest that the whole thing was an even exchange.