I think there's no definate answer to that question as it relies heavily on opinion which varies greatly from person to person. Ideally all film festivals aim for good films to have a chance of winning.

Maybe it's better for you to suss it out yourself, I think you'll be able to find out the dodgier film fests quite easily. If you haven't already, check this site out, it lists most of the main film festivals in australia:

www.australianshortfilms.com/100257.php

Perhaps the most annoying factor is that alot of the larger festivals demand that it be the premiere of your films screening, otherwise I'd say enter as many as you can, so I can see the need to choose the 'best'. Then again, you always can enter as many as you want and if your film gets accepted into one of the better festivals, I don't see why you can't pull it out of the others.