They both cost the same amount of money and for that reason, I'd say it's better you apply for an ASIC. If you need to fly to an alternate, you won't have to worry about whether you're legal or not to land there.
Goes without saying that the sooner you apply for it the better, but 6 months or longer and you'd have to be one of the unlucky ones.
I got my ASIC back in 5 weeks.
http://www.casa.gov.au/fcl/licence/fees.htm