With Refrigerate, Hyper Beam is a significantly stronger STAB move than Ice Beam. However, if it doesn't OHKO an opponent's last Pokemon, you'll need to recharge, and Ice Beam can do more damage in two turns than Hyper Beam can in one. If you feel confident that Hyper Beam won't be a problem with recharge, then go with that. If you don't want to worry about Aurorus' frailty and a lower PP count for Hyper Beam, then go with Ice Beam.