I'm not sure about which type of insulation is best, so can't help there. However I would recommend talking to the tradies that will come around to measure up your house - chances are they will know more than the sales staff that are hired for these promotions.

However just wanted to caution about taking up offers that are advertised. You need to be sure you are using a provider that is registered with the Federal Government. This is for a few reasons:

1. Fed Govt pays registered providers directly - if you use someone that is not registered you can't claim the $$ back
2. Fed Govt registered providers have signed an agreement among many things, not to rip the Govt off.

You can call the Fed Govt hotline on 1800 808 571 to double check that the people you are going with are registered and if they are not, get the details of others that service your area.