A quick summary which is accurate I believe:
Amex Platinum Credit cards are $395/year and include a free domestic return flight (destination differs based on origin). The Amex Platinum Charge Card is $900/year and includes a complimentary Platinum Credit Card, allowing you to have the free flight benefit.
Both the Credit Card and the Charge Card offer good insurance, although with the Credit Card, travel arrangements have to be paid on the card to activate the policy, whereas that is not required with the charge card. I believe that the travel insurance offered under the Charge Card to be exceptional.
The Charge Card provides complimentary membership to Priority Pass for the primary cardholder. This gives you access to lounges around the world, including Virgin Blue lounges in Australia.
It can take a few weeks to arrange the Priority Pass membership and to receive your card, so make sure you apply with some lead time before your departure.
They also have an ongoing promo whereby they reduce your first year membership fee to $600 for the Platinum charge card. You have to ask the call centre for the relevant form or promo code.
Both of these cards offer 1.5 points per dollar spend which are held in an Amex MR account and can then be transferred to a variety of places including Qantas and Virgin Blue.