I don't think that's what you meant. Maybe the Frecciargento is slower?

To the OP: if you book the Super Economy fare, if you miss the train, the ticket has gone to waste. At the Economy fare, if you can get it changed before the train's departure time, you can pay the difference to the Base (full) fare for a train of the same category. If you book a Base fare, double-check on it, but I think you can change it once up to an hour after departure of the train you miss.