For those not too far stretches, I would assume that a Swiss Half Fare Card is probably cheaper. You might also want to consider Saver’s daypasses (non refundable, at varying prices depending on travel date and date of purchase) or the seasonal special offer mentioned here as depending on your travel date. For the trip coming from the airport, a Supersaver’s ticket is not a good idea because you can’t use it in the case of a flight delay, but for going back to the airport if you know exactly which train you are taking, that might be a viable option.