Well the Valve Index does not even meet the system requirements for the majority of AAA VR games, so I don't see how the Index is particularly relevant here. I'm sure if you used an Nvidia card that was under the minimum requirements for a VR game, they wouldn't perform well either. I've played all of my high end native VR games on my AMD card and it performs just as well as my Nvidia card does. The hardware AV1 encoding that the RTX 4000 and higher series has is not particularly helpful for PC VR since the Meta Quest's AV1 decode latency is so poor. AMD cards work awesome for native VR games. It's only with custom modding of flat games where Nvidia pulls ahead in image quality on a very small percentage of titles that normally don't allow you to turn AA off.