Kilda Ste Hilda. It may or may not be better to land gear up, but the specific advice of the Flight Crew Training Manual is as follows:
'If one landing gear is not downlocked, the flight crew must perform the LDG WITH ABNORMAL L/G QRH procedure. In this case, it is always better to land with any available gear rather than carry out a landing without any gear.'
Therefore the crew had no choice as that is the official guidance, presumably because Airbus have considered the various options and concluded this is the best way. Hope that helps.