"I like Dunedin because I can get to spend some time going to Queenstown but Wanganui's event is hard to better," he said.
"Where else can I go for seven days and party every night? The entertainment every night is great and it gives you time to recover."
He said he also liked Wanganui because it was safe, friendly and everything was "very affordable".
"For example at Alice Springs they hiked up the prices but that never happens here. It really is a great long-term investment for your city," he said.
Trewartha said the world Masters Games in Turin later this year was a reason there had been a drop in the number of Australians competing in Wanganui.
"A lot of them don't want to have to do two international flights so opted for the event in Italy."
But he reckons Wanganui organisers needed to do more to promote the NZ Masters Games in his country.
"Get some ambassadors working on it and actively promote the event. If you did then I reckon you'd be overrun with Australians."