There is a smaller margin requirement but the spread is terrible and the ssf trades more like an option contract in my opinion. What ever direction the market starts to move in, the spread will jump huge in that direction making entries difficult. I trade the DIA ssf now and then but for a bit longer time frame than how i trade the YM. I will usually fade moves just a bit to get a better entry. Not very scalpable. I prefer the YM. It is cheaper to trade when you consider your $ return per point and I get better fills. The only way you can get in or out of the DIA ssf instantly is to pay the spread and it is usually way too wide. The YM is my vote. Great for scalping and for trends. I love it. Good Trading All.