You might want to take a look at www.ski.com.au
They have fairly good resort reviews, and if you still want more info, ask the locals in the forum there or do a search of past threads (there have been plenty).
Thredbo does have the largest verticle in Aus due to the lower altitude of the base. This means that if conditions arn't great, the lower half of the mountain turns to slush anyway. It does however have a great villiage atmosphere.
Hotham has the most advanced terrain, but again if it hasn't snowed in a while much of this can be closed.
Don't forget to consider Perisher Blue, which is by far the largest resort in Australia. It has less verticle, but has a higher base than nearby Thredbo so often has more reliable coverage. Plus it's big enough to keep you interested for a while.
Good luck and enjoy your trip.