Quote from oldtime:
It can't be done in a cash account, you need margin to beat the market, there is no other way unless you are the greatest trader of all time.
Check and see how you would have done this year at 80% fully invested long in cash and 20% doing your DCA thing with SPY or ES.
It's hard to beat the index, IMHO it can't be done getting in and out. In a good year a trader will very rarely beat buy and hold, but in a stagnant and volatile year like 2011 a trader can enhance returns trading a small amount of the stash on margin.
But getting back to your original question which nobody answered, I'm still wondering what's better, SPY or ES? Especially if you're trying to DCA in.