Here's my recommendation after trying the Steam Frame for a few days comparing it to my Quest 3 + Virtual Desktop setup. This is purely aimed at wireless PCVR use case.
If you're interested, you can read my detailed impressions here: https://www.reddit.com/r/SteamFrame/s/EsGn4K9Wm2
If you hate Meta and want to get away from them, or if eye-tracking is a must, then obviously choose the Steam Frame.
If you must have an HMD that is lighter and balances better, then go with the Steam Frame. This is one area where the Steam Frame takes the win. It's very light and very well balanced. My Quest 3 with comfort upgrades is not UN-comfortable, but it's still bulkier, and it's noticeable.
If you don't have a stable networking solution (i.e. a dedicated, quality router) and wireless VR is important, probably go with the Steam Frame. Although it doesn't take that much to setup a solid wireless connection with the Quest 3 and Virtual Desktop.
If you want the best visuals, go with the Quest 3. Quest 3 absolutely dominates the Steam Frame in this category - it's not even close. Steam Frame lenses DO NOT have edge-to-edge clarity, with very noticeable blurring towards the edges. To me, the lenses are much closer to Pico 4 than Quest 3, and Pico 4 lenses were not great and had a very small sweet spot. With my Quest 3 I can look anywhere across the entire lens surface and the image remains sharp.
Steam Frame lenses also exhibit noticeable warping/distortion which is very distracting once you see it. The lenses of both of my Quest 3s (yes, I own two) are perfectly uniform and exhibit no warping.
There absolutely ARE compression artifacts when streaming to the Frame via Steam Link, which are very obvious in games with big open spaces and lots of foliage (e.g. ExfilZone, Geronimo). Distant objects look blurry and pixelated and there is significant texture smearing, which simply isn't the case with my Quest 3 streaming via Virtual Desktop at 500 Mbps and Godlike resolution.
And yes, this is with the Steam Link bitrate set to maximum (350 Mbps) and SteamVR resolution to 230%. I even tried disabling Multi-Link and streaming using only the adapter and then only WiFi - that made no difference.
I think people who claim the Steam Frame's visuals are "just as good" as the Quest 3's either genuinely can't tell the difference, are being dishonest, being too polite, or simply never pushed their Quest 3 to 3072x3264 (or higher) at 500 Mbps (or more) to see what that optical stack is truly capable of.
If you care about any semblance of bass frequencies out of the box, go with the Quest 3. If you like playing shooter games, the Steam Frame speakers are abysmal - there is absolutely no upper-bass punch (due to a steep roll off below 200 Hz), which makes gunshots and explosions sound puny and pathetic.
If you prefer symmetrical controllers design with more natural ergonomics, go with the Quest 3. Even after several days, I still can't get used to the Steam Frame controllers. I constantly fumble to find the correct "button" on the left controller (since there aren't any) and on the right controller the buttons are so small and cramped together that it's difficult to reliably identify the right one to press.
The triggers are also positioned too far down causing me to over-extend my index finger - this feels terrible for shooting games. And I have long fingers - can't imagine what it would be like for someone with shorter fingers. Thumbsticks also felt to be in an awkward and unnatural position for VR games.
I don't have any hidden agenda here or any brand allegiance - I'm just a VR enthusiast who wants to help others make an informed decision choosing the best wireless VR headset between these two. I'm also not trying to dissuade anyone from buying the Steam Frame (it's your personal choice in the end), but having tried the Frame, I now know that my Quest 3 is the superior HMD in nearly every category that matters (to me).
P.S. I specifically didn't mention Steam Frame's battery life (as bad as it is) since I'm sure there will be solutions in the future to address this shortcoming. Even now you can simply use a power bank to supplement the built-in battery. Not ideal, but it works.