For those who traded actively--and I mean day trading--what do you think is a better vehicle (in general): ES (e-mini futures) or SPY (ETF)? Commissions at IB are comparable: 500 shares of SPY would run a bit more than 1 ES. But the penny spread of SPY would translate to a 1/10 spread on ES, and we all know that ES trades in quarters. Liquidity would not be an issue for me, as a retail trader whose account is in the 6 digits, and who would consider 4 ES a big position. I was just curious. Thank you.