I will post my old comments about Pico 4 vs Quest 3 to this tread
I changed from Pico 4 to Quest 3. Actually I had both for few moths but noticed I prefer Quest 3. I used Pico 4 only when Quest 3 was out of current and was charging Then I decided to buy headband with battery pack for Quest 3 and sold Pico 4.
Main reason for me were PT and better lenses. Using Pico 4 I could see individual "pixels", good rays and some image warping. Those were really annoying, especially latter warping. Like some black hole in front of picture delicately distorting everything. Using Quest 3 all are pretty much gone. For me visual quality improved, but it depends from person to person. Some did not see any warping or screen door effect using Pico 4. That souds weird.
Actually you will loose some FOV using Quest 3 That's is the only negative thing. I really liked Pico 4 because of larger FOV and better lens overlap (no binocular feeling). You can get larger FOV by using Quest 3 without face cover by means of buying Bobo VR S3 Pro head strap. Worth every penny.
Even though passthrough might be better now using Pico 4 ultra, lenses are the same and problematic for me. There are no real reason to buy Pico 4 ultra.