Well, the resolution is about the same. Valve however chose to implement a diffusion filter in the Index, to combat SDE and pixel pattern. It works very well, I never notice any pixel pattern (unless I actively look for it) on the Index, while in the 5k+ I find it disturbing at times. However this comes at the cost of SLIGHTLY more blur. I noticed it yesterday while doing some more A-B-ing. However it’s very refined and nowhere comparable to the Odyssey+ which has way too much blur. In fact, text looks just better on the Index than the pimax 5k+, letters are more ‘rounded’ instead of more ‘blocky’ like on the 5k+.
I find the index much more immersive than the 5k+ and I’m starting to think one of the factors contributing to that is the diffusion filter they used (next of course to higher refresh rates and no distortion)