Shorter QT time may be more stressful, I use water from my display for my QT water changes, that way the water parameters should be almost identical so the move isnt a big deal. If you have lighting for your QT similar to that of the display you can acclimate it to your displays lighting without moving it around in the display or forcing your other livestock to indure a shorter photoperiod. If the coral needs treatment for infection or say red flatworms, or red bugs in the case of SPS, it can be done there easily.