In terms of loading times, fastest to slowest version is:

PS5 > PC >> PS4 >> Xbox Series X/S (> Xbox One ) >>> Switch

From the footage I've seen, PS5 has easily the fastest loading times, followed shortly by PC. Xbox Series X and S seem to have pretty much identical loading times, but this might get proven wrong with possible further investigation in the future. Switch loading times are the longest, and the difference between Xbox/Switch has the biggest difference by a lot. There's been quite a few performance issues reported on the Switch-version as well, so speedrunning the game on Switch isn't recommended.

The only PS4 footage I found was the version played on a PS5, which most likely affects the loading times. There still was a noticeable difference to the Xbox Series -version, so it's an assumption that the PS4 is faster. I'll update this if other results come up.

I couldn't find any footage on the Xbox One version, so this is just an assumption. If I do, I'll update this.