You have to look at the component weighting in the basket and the relative execution slippage and liquidity costs for doing the individual stocks making up the basket and/or the SPY versus the futures index.
The conclusion is that the index futures will provide more liquidity at the best price versus the physical underlying.
Calculate the slippage costs and the inherent exposure value of the ES best bid/offer compared to the SPY and the point becomes apparent.
The conclusion is that the index futures will provide more liquidity at the best price versus the physical underlying.
Calculate the slippage costs and the inherent exposure value of the ES best bid/offer compared to the SPY and the point becomes apparent.