The difference between updates and patches seems to be that updates change the version number on the about dialog and patches don't. If installed via GetIt, patches are listed in the registry and will be shown in the about dialog as an additional information, but that does not happen if you don't use GetIt for the installation.
Both can switch some executables, which then will get a new version number, but you have to know for which executables to look to see that difference.
I have code in GExperts that identifies the current update and patch level in case some workaround or fix is necessary. I thought about making a small stand alone tool from this, but never came around doing it. That code is in
https://sourceforge.net/p/gexperts/code/HEAD/tree/trunk/Source/Framework/GX_GetIdeVersion.pas
In case anybody is interested.