This video compares the visual fidelity of the Quality and Performance Mode of Mouse P.I. for Hire on the PlayStation 5 Pro.
For this comparison, the Diffusion and Film Grain Effect settings are both set to zero.
You can find the video below:
As you can see, Quality Mode looks sharper than Performance Mode. The tradeoff is that Quality Mode targets 60 fps, while Performance Mode target 120 fps. For a first-person shooter, frame rate may matter more to some players than a higher resolution.