Small Limited Performance Test of 5080 vs. 5090 for VR Using FCAT VR
**All useful info at a glance is in the table below if you want to skip the preamble and get straight to the meat.**
By chance I temporarily have both a 5080 and 5090 FE on hand, and wanted to take the opportunity to test VR performance on both cards since I haven't found many (any?) direct head-to-head comparisons using actual FCAT VR data (RIP BabelTechReview's VR reviews whatever happened to those). Most of what I see on the web is either reviews of 1 card or the other with only constrained FPS data, or is a review using only flatscreen games.
Many games in my library that I wanted to test straight up did not work with FCAT VR on my system unfortunately (tried HL:A, Into the Radius, Cyberpunk VR mod, and a few more with no luck), so the test is limited to Skyrim VR, Moss Book 2, and Wanderer, but I feel those are at least enough for a sanity check of VR performance.
Here is the datasheet of the results using FCAT VR :

Unconstrained FPS compared at a glance:
Quest 3, VD Godlike Resolution & **100% SteamVR Resolution (3072x3216)**, SteamVR set as OpenXR Runtime
|Game|5080 Unconstrained FPS|5090 Unconstrained FPS|Difference %| |:-|:-|:-|:-| |**Moss Book 2** (Default Settings)|239.20|376.84|\+57.54%| |**Skyrim VR** (Default Settings)|143.50|223.52|\+55.76%| |**Wanderer** (Max Settings, No Upscaling)|241.67|369.48|\+52.88%|
Quest 3, VD Godlike Resolution & **200% SteamVR Resolution (4344x4616)**, SteamVR set as OpenXR Runtime
|Game|5080 Unconstrained FPS|5090 Unconstrained FPS|Difference %| |:-|:-|:-|:-| |**Moss Book 2** (Default Settings)|132.05|207.12|\+56.85%| |**Skyrim VR** (Default Settings)|75.17|122.47|\+62.92%| |**Wanderer** (Max Settings, No Upscaling)|139.43|227.20|\+62.95%|
Quest 3, VD Godlike Resolution & **300% SteamVR Resolution (5320x5652)**, SteamVR set as OpenXR Runtime
|Game|5080 Unconstrained FPS|5090 Unconstrained FPS|Difference %| |:-|:-|:-|:-| |**Moss Book 2** (Default Settings)|87.04|144.78|\+66.34%| |**Skyrim VR** (Default Settings)|27.10 (DNF)|81.51|\+200.77%| |**Wanderer** (Max Settings, No Upscaling)|97.51|153.66|\+57.58%|
Quest 3, VD Godlike Resolution & **500% SteamVR Resolution (6868x7296)**, SteamVR set as OpenXR Runtime
|Game|5080 Unconstrained FPS|5090 Unconstrained FPS|Difference %| |:-|:-|:-|:-| |**Moss Book 2** (Default Settings)|55.06|96.28|\+74.86%| |**Skyrim VR** (Default Settings)|N/A did not boot|N/A did not boot|N/A| |**Wanderer** (Max Settings, No Upscaling)|42.69|97.08|\+127.41%|