[vintagedave]

I found Windows 10 rapidly gets slow, the slowest being opening the Start menu and right-clicking taskbar buttons. Possibly the menus are a new implementation: all the new menus etc in Win10 and 11 seem to open slowly or repaint slowly under Parallels.

Windows 11 so far feels slightly faster in terms of responsiveness and UI. However my typical performance benchmark is to run a build of the software stack I work on, which takes 1.5 hours (good machine) to 3 hours (slow or low-end VM.) On the same VM, upgraded from Win10 to Win11, this build slowed from about 2:45 to closer to 3 hours. Minor over such a long timeframe, but it does show the OS is definitely not faster.

[accrual]

For the Windows 10 start menu you may benefit from disabling it's "online" component. On my system it makes opening the start menu and searching for items nearly instant:

    [HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\Windows\Explorer]
    "DisableSearchBoxSuggestions"=dword:00000001

While you're there, you can also reduce menu delay:

    [HKEY_CURRENT_USER\Control Panel\Desktop]
    "MenuShowDelay"="20"

Windows 10 really benefits from tuning. I periodically run WDP and O&O ShutUp10++ to turn off various telemetry things and my system is super snappy (870 EVO, 4th Gen i7, 32GB, 1080Ti).