Gold Coast - the land of golden sand, amusement parks and excellent weather. Yet its so touristy its almost fake. Gold Coast is like the teenage stage of Australia - you go there to have good, innocent fun (or non-innocent - who am I dictate your terms. The must see feature is Australia Zoo - I went when Steve Irwin was still alive and he did live shows. The Zoo allows more interaction with the animals and zoo keepers stand around with animals from birds to snakes and you can cuddle Koalas. But if you have limited time you can skip Gold Coast.
Sunshine Coast is the home of the beaches and night scene. There is the bed bar (yes, instead of tabels they have beds...). There is Noosa Head and Tail (imagainative really) with great lakes and lagoons. The seafood is amazing. The best things around that part of Queenslsand would be Cairns and The Whitsunbday Islands.
Try it factor: 4/5 unless you really like amusement parks.