Celtic are better quality by a fair way IMO. Uggs are not Australian (it's a US company, and they use Chinese sheepskin. All you pay for is marketing.)
The funny thing is, Australians think they're slippers. They think wearing them in public is bogan. (Untranslatable, though if anyone's ever seen Emmerdale the Dingles would qualify. Too... bogan even to count as chavs.) I'm glad to live in the UK so I can wear them to the supermarket and not get stared at!