I can't speak to the Index as I have only used Odyssey, Rift S and Reverb.
The Reverb by far has the better resolution and clarity.
Some simple examples:
Rift S - F15 fuel, harder to make out, Reverb much clearer
Reverb - BVR I can make out a single bandit dot contact in my target box at 20+ nm. Rift S was more of a blob and I couldn't see it out that far much less detail.
Lastly I like to use my F15 refueling, Rift S then refueling lights were not clear at all I would have to zoom in for clarity. With Reverb it's clear with no zooming.
All the text is very readable not blurry edges.
Now, again I havent used the Index, but just go look at the spec sheet the Reverb resolution blows it away.
I get all this with good frameratea - no messing with some third party Oculus Rift software. Simply setup SteamVR - for me, slider is at default reslotion, no messing around with "200%" - just don't need it. In games DCS, PD 1, MSAA 2x, extreme distance on. Solid 45 with motionreprojection on, 90 with it off.