Traded Big S&P500 back in 80s/ES currently, can do size, has same personality all these years, Herky/jerky. NQ is different, more forgiving to me as far as if I get in wrong or need to get out, it has a little less follow though during chop, but takes off in fast market conditions, cancel targets.....Mini Dow is strange market to me, but has some of the deepest retracements of all the Indexes, very reoccurring patterns though. I risk less trading the Dow but so are the targets. The Russell for me is the only index where I risk less than the targets and it trades similar to NQ. But overall I am a Scalper, so I view the Indexes much differently than trend trader.
But what matters most, which of the three can you trade, they all have different personalities.