Simon spoke about this in his show last night. CFD, I think. SSF, you pay the interest for the full period to expiry, whereas CFD you only pay for the interest for the holding period. That's all I've picked up from the docs - hopefully more will chime in.
CFD's by a long margin, and they are easier to trade and manage your slippage costs. Note however, that OST CFD's are only cheap if you are trading in positions in excess of 200k, because of the flat brokerage fee charged on top of the commissions. Anything less than that, and your brokerage fees reach up to 0.8% each way
I guess the real question is "which makes the higher profit?", rather than the lowest costs. I haven't really studied how the interest works on SSFs, but as I understand it, with a CFD the market maker buys the share and so effectively gives you a loan to cover the cost and you currrently pay 9.5% interest on this loan, whereas with an SSF the market maker doesn't actually buy a share, so there is no loan that needs to be serviced, although there is some interest in teh pricing of teh SSF (as I say, I haven't studied the theory behind this yet). However, I have taken 5 SSF trades that I have done over the past couple of weeks, and calculated what my profit would have been if I had done the trades via a CFD, and the SSF trades gave more profit in all cases. My sense is that the CFDs get worse the longer you hold them (because interest is added everyday), and this could represent quite a risk, eventally wiping out any chance of a profit (well the share price would have to rise 9.5% + .35% + .35% + R57 + R57 = about 10.5% over a year, so about 1% for every month you continue to hold the CFD. Note that the flat fee of R57 each way is actually not that relevant in comparison to the .35% each way and the interest at 9.5%. My results were: Share Days held Exposure SSF Profit CFD Profit SOL 5 114,400 1,467 1,324 BIL 8 39,600 1,135 1,122 GFI 7 27,750 1,606 1,605 MTN 7 62,000 2,338 2,330 GFI 16 28,500 1,061 783 Hope the table keeps its formatting when I push send!!