I have to agree with Daniel. In my line of work, which involves motion design and visualization where visuals are scrutinized closely, the mandatory use of Lumen in version 5.4 has resulted in a noticeable decrease in quality. Both reflections and shadows appear less accurate compared to the deprecated hardware version. This is especially apparent on surfaces such as cars or materials that verge into glossy territory (roughness levels of 0-0.25).
Previously, I could adjust quality/performance using the number of rays, but with Lumen, I only have the quality slider and a few mentioned cvars to attempt to enhance the appearance. The persistent moving noise, especially when attempting to improve reflection quality, is particularly troublesome in my projects. A lot accuracy is also lost in relfective surfaces with subtle roughness or normal variation. They appear much rougher than they should. This becomes a big issue when I’m trying to replicate my clients materials, as it doesnt represent them closely enough.
It’s a real shame because there are lots of great reasons to use 5.4, namely nanite displacement improvements, the new motion design mode and the big improvements to sequencer. A real dilemma for me almost forcing me to stay on 5.2/5.3. I havent time to provide screenshots, but they are similar to Daniels, just wanted to chip in with his worries.