Unless iinet can garuntee tha you'll be on an iislam I'd go westnet. If you're not on one of their dslams you'll end up paying alot for 1500/128.
My personal story involves 4 weeks of f**king around with telstra and iinet trying to get them to talk to each other to fix THEIR own problems (invalid database entry) until I said f**k it and rang westnet, was all sorted within a few hours.