My 2 cents worth - CFD providers are good for shorting stocks, though there is some interest gouge no doubt. Also ok for small size index exposure, trading without stops. When the futures market is closed, the CFD can do anything. Also trades away from futures at times when the market is open depending which way the market maker is set. If you can trade a full $25 contract , go with IB or one of the ASX futures members ( not sure which of them still deals retail). Margins will be much larger, but you are not at the mercy of a market maker. The SPI futures contract will trade in line with the ASX 200 ( plus/ minus forecast carry costs, borrow costs and dividends) as the arb players are continually active to ensure this is the case.
(20min delay)