Cutten, Look at the markets like a Track & Field meet. Some like the hurdles, some like the shot put, some like the sprints, some like the long jump et cetera. It's not so much which is better. It's more what you want to do. There are traders (retail and institutional) making a living in any areas of the markets...Eminis, ETF's, Eurex, Forex, Bonds, Equities et cetera. You just need to sit down and figure out which one(s) you want to compete in... Then fine tuning your ability into a specific area. NihabaAshi
Actually you can short e-mini's in IRA whereas it is not allowed for ETF's. So one more advantage for mini's. But on the plus side for ETF's are, scaling, size of hedge relative to one's position, liquidity on options (esp. on cubes), and maybe low commision, as you and others pointed out.
The futures have more advantages than the ETFs in my mind as well but it depends what you are trying to do. With ES there is such high volume on the bid and ask that it's tough to get executed some times so I end up doing market orders. The volumes on the SPY bid/ask are smaller. Also, when the bid/ask spread is 1 or 2 cents, the slippage is less on 500 shares SPY which is equvalent to 1 ES contract.