damnnn man.. thats a hella far trip from perth to the US...
Both places are great.
Everything in Vail is expensive but they have some nice bowls in the area. If you have a car and time make the drive to Breckenridge ( about 30 min) and go ride over there too. Breck has more restuarants and clubs/bars then vail.
In Park City just have fun! I love Park.. ride both park city and the canyons..plenty of terrain to be had there. Park citys night life is great.. lots of clubs and bars..
have a great trip