Essentially I agree with Oz's comment above.
My experience is limited to the Snowy Mountain ski fields of Perisher Blue ( PB), Charlotte Pass and to a limited extent Thredbo.
However, I would also like to add that PB seems to be on the ascendency over the other ski resorts for example .....with more modern chairs and extensive snow making ( thanks to Kerry Packer having deep pockets).
PB also has 50 lifts covering the ski fields of Perisher, Smiggin Holes, Blue Cow and Guthega.
Its so big it can cater for every level of skier.
I think Thredbo has more blue/black terrain.... so it suits the higher level skier and those who like the extensive accomodation and night life options close to the snow.
If I feel lazy, I go over to Charlotte Pass ( but can still only get there via a snowcat ( 40 minutes) out of PB ) and cruise their slopes.
Charlotte tends to have better quality snow and less snowboarders.
The queues are almost non existent even in peak season.
Its more a blue level resort with some blackish runs
I haven't been to the Victorian snow fields ( eg Buller )so I can't comment on those.
Lastly, in respect to the fun factor, because the snow season is not as extensive/heavy falls of snow as in say Nth America or Europe that the terrain in Oz that you ski on is different from one month to the next.....in the early season, on some runs, you ski around large boulders etc at a resort but latter in the season, at the same resort, the boulders etc are completely covered and the terrain can therefore be less varied and not as much fun. I like to ski early in the season.
Last one down the slope is a dirty snowball!!