Bitcoin Core 28.0rc1 (both pre-built and self-built binary) on Windows 10 synchronizes much slower than 27.0 after around block 120,000 when blocks stop being almost empty. I'm running with default settings (dbcache=450, pruning disabled).

Time to synchronize to block 300,000: (measured around 10 runs each, alternating between the versions)
27.0: 695 seconds
28.0rc1: 2760 seconds

Running the Linux pre-built binary in WSL doesn't show the slowdown, so it's probably limited to Windows.

I'm going to bisect this, but that will definitely take me a while. If anyone suspects a commit/PR that I should look at first that might help. I've bisected this down to #28052, for more details see #30833 (comment).