I think you slightly misunderstood my intent. Im saying that to match the coronaPhysical metal in with a physical material i have to set the physical material IOR to 2.5-3.
Maybe it would better if you would show side by side comparison with the same settings then, i.e. metal mode is on, metalness is mapped.
Coronas metal mode locks the IOR of course, which is physically incorrect anyway because metal ior has a fairly broad range range and absolutely cannot be defined by a single arbitrary number. I would hope this is something that gets changed in future so we can get physically correct metals.
You can switch to complex IOR mode which is more physically correct for metals.
Its the Nvidia GPU denoiser in IR. It just seems to handle the physical materials faster for whatever reason.
Maybe try to switch to Intel AI denoiser, i think it shows slightly better results than Optix. Anyway the difference in denoising quality in your example is really huge, perhaps it's worth to post it as a bug?