I have the s20 ultra and the OnePlus 8 pro both. Signal, battery life, and display options are better on the OnePlus. Cameras are about equal for point and shoot which is the majority of my photography.
I have the S20 Ultra and it sits unused because I love the OnePlus 8. Because I miss wireless charging, I am now upgrading to the OnePlus 8 pro. Going to see if I can for a sucker - umm, I mean buyer - for my ultra.