Open the platform and the indices run down the screen. American, European, Japanese, all of them moving.
The first thing most people ask is which one moves the most.
That is not the wrong question. It is just in the wrong order.
Where most people get the first step wrong
However much an index moves, if it moves while you are in a meeting, stuck in traffic or asleep, it has nothing to do with you. You never see it happen, so all you can do afterwards is look at the chart and imagine what you might have done.
If you hold a full-time job, the first condition when picking an index is time. Not volatility, not hype, not whoever is talking about it.
Once the hours fit, you have earned the right to weigh everything else.