for third party I can see it both being often just an advantage in load times (and performance, in the sense of reducing stutters or pop in/streaming issues)
but I can see them also using it to push higher detail than PC/Xbox, but not in a drastic way, think of some settings on PC on ultra as opposed to high (or medium), it costs a lot of hardware to get it but it's not always obvious for the player.
I do think that, this advantage for the PS5 could make a larger impact than the "20%" (not really, it's complicated) faster CPU/GPU ram speed advantage of the Xbox.
but with the apparent lack of Sony focus in RT, maybe the Xbox has much better ray tracing performance/solution? that could be a even more significant thing!!?
for the PC, I think it's safe to assume people playing the next gen games in 2021 should have an SSD, the problem is, a much slower one, even the 2.4GB/s of the Xbox is not a safe to assume speed on the PC at all...
but then we still have many games at the same time targeting the old consoles with their 5400RPM drive as multiplatforms, so who knows...
it sure could lead to some bad experiences, like 5 minutes of load times in those and instant load transitions on the new boxes, with much higher quality.